 It is 1952 and the British Railway is in turmoil. One train has crashed into another in a thick October morning fog leading to a third collision. Even after over 100 years of industry development such disasters are unstoppable in poor visibility. Safety is ensured by the driver being relied upon to modify their operation of their train for the prevailing conditions. Surely this kind of tragedy can be designed out of the industry. The disaster will hasten the implementation of an automatic type of warning system that will advise the driver of the state of the signals ahead even in poor visibility and if ignored would intervene bringing the train safely to a stand. These echoes within the industry would be a mirror from the past 48 years later in the wake of the elaborate growth disaster but instead of praising the system criticism of its shortcomings would be the focus of the industry. Today we're looking at the Harron Wilson disaster the UK's second deadliest rail accident. As such I'm going to rate this subject here six on my disaster scale but here eight on my legacy scale as the historical significance of this event can't be underestimated as it would influence railway safety across the world. Harron Wilson is a train station 11 miles and 30 chains from London placed in modern day Harrow London borough but in the 1950s it has yet to become absorbed by the UK's capital and as such is firmly within Middlesex. It is a busy interchange between intercity, suburban and metro services. As a side note in case you're wondering a chain is a form of length measurement and 80 of them make up a mile. The station serves the west coast mainline with its fast services to Scotland as well as the Watford DC with its trundling London transport Bakerloo Line trains and their British Rail DC counterparts. Because of this during the morning peaks a large number of passengers using the interchange keeps trains and platforms busy a site that continues to this very day. Harron Wilson in the 1950s had seven platforms one and two for the north and south DC and three and four for the north and south fast and five and six for the north and south slow. I will say though as this is a British rail station and infrastructure compass directions aren't usually used to describe the line direction instead we'll use the standard nomenclature up the London directions so that will mean south is up and down is for away from London so north is down so just to clarify one is down DC two is up DC three is down fast four is up fast five is down slow six is up slow and seven is for the eventually abandoned Stanmore branch line. The fast slow and BRDC services on the London end terminate at London Euston. London transport Bakerloo Line trains leave the DC at Queens Park where they continue underground to Elephant and Castle. Train movements around the station are controlled by two signal boxes Harron Wilson box one and box two the latter is for the DC lines and won't really play much of a part until later on box one controls both the fast and slow lines in and out of the station and this takes the form of semiform mechanical signals with colour light distance signals and this leads us to the part of my railway videos that I think I enjoy making more than some of you enjoy watching British Railway Signalling Principles. The method of working in use at this time was that of absolute block signaling like most railway signal concepts it uses one train in one block at one time but unlike track circuit block signaling used in most UK railway lines today it relies much more on multiple signals and signal boxes to safely signal a train along the line and to communicate with one another the location of each train as the working principle was invented before proper train detection its safe operation depends on the strict observance of rules rather than relying on continuous train detection equipment but before we go deep into its working practices let's look at what the signals do and what they mean to the driver this is a semaphore signal it has on the west coast mainline two positions which is shown like this as horizontal and off shown here as diagonal on is the same as a red signal and therefore is a stop indication to the driver do not go past it as there's potentially a train ahead off means the same as green or a proceed signal to give advance warning of the state of the stop signal ahead a distant signal will be provided this semaphore is similar but yellow and when on it tells the driver that the next signal could be showing danger and that they must be prepared to stop when in the off position it means that all the signals in the next block section are clear because the distant signal is only an indication of the next signal there is no requirement to stop it instead of a semaphore style distant signal a color light can be provided this can show green for the next signal is at green or off and yellow for the next signal is on or at danger all distant signals are placed at a braking distance from the next stop signal there are other signals for junctions and shunting but for the purpose of this video we won't delve into that let's look at how the basic operation of absolute block signaling works a line is split up into block sections and each section is under the control of its own signal box each signal box will have at least one distant one home and a starting signal the section of the line between the outermost home and outermost starter is called station limits and a signaler can move trains within this area without having to see if the section to the rear or advance is clear let's draw here two signal boxes and two running lines for an up and down line if a train is to travel on the up towards signal box a from signal box b the signaler in b must contact signal box a this is done via a bell code if the block for box a is clear then they will set an indication on a machine called a block instrument to tell the signal in box b that the line is clear in reality the process is much more complicated using various bell codes and indications that the line is normal that there is a train on the line or clear but for this video i'll try not to get too carried away okay so if box a's block is clear they will then accept a train from box b by indicating line clear and then box b will clear its starting signal allowing the train into the block section in our case on the up once the train has fully passed the starting signal the starter will be replaced to danger the train would approach the distance signal for box a's home signal if all the signals for this block controlled by box a are showing a proceed then the distance signal will be in its off position and in our example you can see it is once the train is past the home signal for box a and the signaler has observed the full length of the train past the signal box and they have seen the train's tail lamp indicating that no part of the train remains in the section to the rear the signaler will then replace the home signal to danger and indicate to box b that the train is out of the section then b can accept another train and the process can carry on harron wilson is a little more complex as it has multiple home and starting signals but the signaler has total authoritative control over the trains within the furthest home signal here and the most advanced signal here this allows trains to stack up outside stations safely by allowing the train up to the home signal if there is a train on the platform the distance signals a colour light style on a gantry over the fast and slow lines the signals in the area are interlocked using track circuits stopping the signaler from clearing the distance signals or any main signals if the associated circuit is occupied but with all this processes you may have noticed one thing lacking the actual means of stopping a train as this system relies on the driver being on the ball and following the rules an incident could happen not maliciously on the part of the driver but by loss of concentration or lack of root knowledge which could result in a collision especially in the case of poor visibility as the signaling indications are purely visual well there was a system in place to tell drivers of dangerous signals in poor visibility and that was detonators basically a very small explosive device attached to the running rails that would be set off if a train went over it creating a very noticeable bank obviously not strong enough to damage the railhead or the train wheel though but if the driver hears detonators go off and they haven't been told otherwise for instance in the case of assisting a train with authority already given they must immediately stop and this leads us on to a foggy morning on the 8th of October 1952 the morning of the 8th was like any other albeit with many late running trains due to the thick fog that had descended upon the area a train berthed in the upfast platform 4 at 8 17 a.m seven minutes late it was the 7 31 a.m Tring to Euston local passenger train consisting of nine carriages carrying approximately 800 passengers this was hauled by LMS Fowler 264T class steam locomotive there around 800 passengers on board more than normal but this was due to cancellations of other services the service from Tring had travelled towards Harrow on the up slow lines but had been routed onto the upfast to allow for empty stock movements on the slow line local services during the morning peak have priority over the sleeper express trains and as such it was well known by drivers that if trains are running late the fast services will mount up further delays as the local service concluded its platform duties the starter and advanced starter signals were cleared for the train to continue its journey and this was at approximately 8 18 a.m but due to the train still occupying the platform the upfast outer and home signals were kept at danger and due to the track circuit interlocking system they cannot be cleared by the signaler until the local train is departed thus offering signal protection to the rear the 8 15 p.m perf to Euston night express was an 11 carriage sleeper train carrying approximately 85 passengers and was hauled by LMS coronation class locomotive called the city of Glasgow the locomotive was one of the most powerful at the time in the country and was making easy work of its mix of wooden and steel constructed coaches the perf express arrived at crew at 402 a.m 13 minutes late it was booked to stand for 16 minutes to load off passengers and luggage the train left crew at 4 37 a.m 32 minutes late and 19 minutes after the 10 20 p.m express from Glasgow which had passed it while standing in the station the driver of the perf train made up time gradually catching up to the ex-glasgow train until whatford north box the perf train was held due to the glasgow train negotiating the 15 mile an hour restriction through the whatford tunnel it restarted roughly at 803 a.m seven minutes after the glasgow train had passed the tunnel the perf train made slow progress through the tunnel itself again due to the speed restriction meanwhile the local service on the slow passed through the tunnel and stopped at whatford at around 804 a.m the local departed at 806 a.m and headed towards harrow and wilson stopping at hatch end en route on the slow whilst this was happening harrow box one set up the route for the local train to travel across to the up fast platform which then held the outer home and home signals at danger stop as i said earlier the local train birthed in the up fast platform at harrow at 8 17 a.m as the local moved onto the fast line the perf train was trying to make up time further north also on the fast it passed hatch end at 8 17 a.m at which time the latter had just arrived in the up fast platform at harrow as the train approached a colour like distance for harrow and wilson showing caution yellow the driver did not react this meant that the fast outer home signals were at danger the train was traveling between 40 and 48 miles per hour the perf train passed the outer home danger stop signal and then carried on past the home signal also at danger this was the signal that was protecting the local service on platform 2 it ran over and damaged the points that had been set from the movement of the local from the slow to the fast line seeing that the train was not going to stop the signal at harrow number one placed detonators on the rail but the disaster was unavoidable a minimal emergency brake application was made on the perf train just seconds before it went into the rear of the local train the local train was pushed forward around 20 yards with its rear three carriages being obliterated this was due to the last two being made of wood and were subsequently shattered and the next steel body carriage ends up being crumpled like a tin can the leading two vans and three coaches of the perf train smashed up behind and above the locomotive obstructing the down fast line the 0800 Liverpool express service was delayed leaving euston this was due to a minor vacuum leak which was quickly remedied five minutes after its book departure time the service was formed of two locomotives at lms jubilee class called winwood islands and an lms princess royal class called princess and the two locomotives were pulling a rake of 15 carriages carrying approximately 200 passengers due to a large gap in headway in front of it the Liverpool bound train was making good time on the north bound down fast line with clear signals it was heading at line speed towards harrow but the inner home signal on the down fast was put to danger by the signal but there's no way for the Liverpool train to stop in time the leading locomotive plowed into the perf locomotive at 60 miles an hour the leading seven coaches plus a kitchen car from the Liverpool train shot forward by the momentum overriding the existing wreckage and piling up above and around it several coaches hit the underside of the station footbridge tearing away a steel girder with it the perf locomotive was completely buried under the 45-yard long wreckage some carriages were pushed across the dc line shorting out the up traction current was subsequently switched off and both harrow signal boxes sent out an obstruction message to signal boxes on the up and down dc and west coast mainlines an emergency call was sent out to local fire brigades and the first responders reached a scene at 8 22 a.m the wreckage was a mangled combination of wood metal and the dead and injured many doctors in the area upon hearing the collision attended to offer assistance along with many other locals nearby assistance was provided by doctors and a medical unit of the united states air force based five miles away at ref south ryslip including the soon to be named angel of platform six abbey sweet wine who helped to triage the wounded before they were put onto an ambulance all lines were shut including the relatively unaffected slow as the wounded were evacuated via the good yard once the living were extracted the slow lines were reopened on the 9th of october and to assist with wreckage removal the electric lines were used to transport cranes the dc itself would in turn be returned into service on the 11th of october the wreckage of all three trains were recovered in an impressively fast time with the fast lines opening on the 12th of october the death toll from the crash would be the highest on the railway in peacetime at 112 102 of whom died on the scene with 10 later on in hospital both the firemen and the driver of the perth train were killed as well as the driver of the liverpool trains lead locomotive but that wasn't the total human cost 340 people were reported as injured of which 183 people were given treatment for shock and minor injury at the station and 157 were taken to hospital with 88 being hospitalized after the lines were reopened swiftly and the dead were buried the cause of the disaster could be officially investigated what caused the perth train to miss the indications of danger ahead with it being held by a train at whatford north box the knowledge of delayed express trains taking a lower priority to local trains and three signals of which pointed to a train ahead sadly due to the era the trains didn't have black boxes and with both firemen and driver killed we can only speculate but this was the same brick wall presented to the accident investigators for the lieutenant colonel grs wilson ministry of transport report investigators scoured the wrecked locomotives and found the vacuum brake valve on the perth train was in emergency and combined with eyewitness testimony hinted towards the brakes being applied not long before impact around the same time the inner home signal or the local train could be visible this was further exacerbated by the fog which although at the signal box was further than the minimum distance required for normal working was actually quite patchy near the distance and outer home signals investigators tested the signaling and points equipment at harrow box number one and it was found to be in working order apart from the points that were smashed up in the accident a standard post mortem was carried out on the perth driver and nothing medical was highlighted and at his earlier medical when he passed out as driver in 1946 saw no problems with his sight and general health the report written by lieutenant colonel grs wilson pointed the blame on the driver blame on the signal was squashed when timing showed that the signal couldn't have been put back on the perth train this was because if the distant signal was showing green then the line ahead is clear hence being able to proceed at line speed which could have explained why the perth train did not slow down but this couldn't have happened in the time between the approach to the distant and the local train getting the signal on to the up fast what was strange that was from the guard's eyewitness account that the perth driver had been working cautiously all the way from crew and he adhered to the dangerous signal at whatford north and followed the correct speed restriction through the whatford tunnel the only suggestion was that in the fog he had relaxed his concentration and missed the distant signal whilst looking for it in the fog he was looking at the wrong height as a distant and outer home signals were at different elevations in doing so he then missed the outer home signal and thus ended up going past the point of no return clearly from the driver's record and comments about him that he was indeed a conscientious driver who didn't set out to cause the free train collision and this brings us onto the inherent issues with the british railways of the mid 20th century that is preventing an accident mechanically or electrically which would mitigate the shortcomings of human train operation the event brought around the question of automatic train protection systems which even though wasn't installed on the trains in question wasn't a completely alien concept in 1952 you see a system called automatic train control was in operation on the great western mainline as early as 1905 and this made use of a ramp that moved a spring loaded current shoe under the locomotive this was set off a warning in the driving cab that had to be cancelled otherwise the emergency brakes would be applied if the signal was clear the ramp would be de-energized and the warning would be replaced by a bell and the driver wouldn't have to acknowledge this this system would thus tell the driver via an audible warning of the state of the distant signal in response to the harrow crash this system was developed further through a nationwide rollout a non-contact method was employed based on magnetic induction and was renamed aws or automatic warning system a visual warning was also added to the system and rollouts began in 1956 we'll never know for sure if aws would have prevented the disaster but it is likely it would have alerted the perth train driver of the danger ahead this is a plain difficult production all videos on the channel were creative common attribution share alike licensed plain difficult videos are produced by me john in a currently cold and wet corner of southeast london uk help the channel grow by liking commenting and subscribing check out my twitter for all sorts of photos and odds and sods as well as hint at some future videos i've got patreon and youtube membership as well so check them out if you fancy supporting the channel financially and all that's left to say is thank you for watching