 It's Christmas 1953, and New Zealand is mourning a tragedy. An intercity train from Wellington, New Zealand never arrived at its destination, Auckland. The missing train was a victim of a flood, which caused a bridge collapse across the Tonga Eau River. 151 would perish as the train was plunged into the river below the bridge. The event would go down as one of the worst in New Zealand's history, and as one of the most unfortunate turn of events, as if the train was just a few minutes earlier or later, then disaster could have been averted. Today we're looking at the Tongiwai disaster, and I'll reveal my ratings at the end of the video. So let's see if we'll both agree on the rating later on. The North Island Main Trunk is the main railway line on New Zealand's most populous North Island. The line connects the country's two main cities, Auckland and Wellington. Completed in 1908, it is a marvel of Victorian and 20th century engineering. The line spans rivers, climbed mountains, and passes over vast viaducts. One such crossing is near the small rural village of Tongiwai on the Funga Eau River. The river flows down the mountain side from Crater Lake for approximately 8.5 miles in an easterly direction. Then it turns to the south at the bottom of a fan, runs more or less parallel with a road called the Desert Road for approximately 6 miles, and then in a south westerly direction towards Tongiwai. The total distance to Tongiwai is approximately 25 miles. The river flowing down from Crater Lake created a risk, and that was erosion of its fragile ash banks, which in turn would release large quantities of water down the river channel. The violence of the flow would also take with it large quantities of material, creating a lahar, a violent type of mud flow composed of a slurry of pyroclastic material, rocky debris and water. Needless to say, this can be horrendously destructive, washing away anything in its path. The river was spanned by bridge number 136. It was built around 1906 by the Public Works Department. The bridge was built to a generic standard design used elsewhere in the country. It stood at a length of 198 feet and made use of steel construction supported by eight concrete pillars. The spans consisted from north to south of 122ft, 244ft and 422ft plate girder spans. The bridge design would be criticised later on in that the piers had insufficient foundations but we'll come back to this later on. The bridge would suffer a number of damages throughout its working life, which required repairs to its foundations and piers. The first of such damage occurred in 1925 when a 9ft swell made its way along the river, causing a scour on pier 4's upstream side above its footing. This caused the track on the bridge to be misaligned and resulted in a half inch movement of the structure. To fix the damage, rocks were placed into the scour, but this wouldn't be the last time the bridge would suffer some damage. Just over 10 years later, in March of 1936, the Foreman of Works reported another scour at piers 3 and 4. He recommended 15 wagons of stone for protection. This work was completed on 18 June 1936. Pier 3 would be damaged yet again in February 1944, after a flood and whirlpool scoured a hole 10ft in diameter and 3ft deep on the upstream side of the pier. In June 1946, engineers suggested placing 8 5t concrete protective blocks in the vicinity of pier 4 to offer protection from floods and debris. The project was completed in July the same year. The bridge was closely monitored for the next couple of years, but no other issues were reported, which leads us on to train 626, departing Wellington on route to Auckland at 3pm on the 24th December 1953. Train 626 consisted of a Ka-class steam locomotive hauling 11 carriages, 5 second-class, 4 first-class, a guards van and a postal van. That evening, the 467.3 tonne 704ft long formation was carrying 285 passengers and crew. Many aboard were holidaymakers and as the evening set in, many had settled down for the night. At around 10.20pm, the train passed through Tangiwai. That's what eye witnesses on the station platform thought to be slower than the usual at around 40mph. The reference to line speed was 50mph. Apart from it being a little slower than usual, nothing else out of the ordinary could be seen as a locomotive and its rake passed through. Just one mile down the line was Bridge 136 and its span over the Fungiiyu River. As the train approached the Tangiwai end of the bridge, the engine crew saw a man alongside the track waving a light. Strange, they thought, but soon enough the reason became apparent. As the headlight of the locomotive washed over the bridge ahead, a section of the track was missing. But what couldn't be seen in the December darkness was that a whole section of the bridge had completely failed, sending some of the structure into the river below. Immediately the driver and fireman applied the emergency brakes, but it was too late as the train couldn't stop in the distance of available track. The locomotive and its tender and the first five carriages went careering off the bridge, plummeting into the river below. The remaining three first class carriages, the guard's carriage and postal carriage remained precariously on the track. Bill Ellis, the man who was waving the light by the side of the railway, approached the guard and explained what he had seen. The two men made their way to the sixth carriage, the first first class carriage, which by now was teetering on the edge of the damaged track, and attempted to evacuate as many passengers as possible. They with the assistance of another passenger managed to evacuate 24 people by smashing out the windows. One person wasn't so lucky as the coupling of the carriage failed, resulting in the carriage rolling into the river. 148 lives were lost to the river, including the driver and fireman. 22 of the victim's bodies would never be recovered. Five miles away, the Waiiru military camp dispatched soldiers to assist in rescue operations, along with rescue teams. By midnight, the first survivors were evacuated to Waiiru. A few hours later, the first of the dead were recovered and sent to a makeshift morgue. More of the dead would be pulled from the river downstream by locals and farmers, giving a grim awareness of the disaster. 60 of the victim's bodies would be recovered in such ways, but the unrecovered victims are thought to have been washed out to sea. As many awake for the Christmas morning, the news is broadcast across the country and the public is made aware of the full scope of the tragedy. With so many dead and an apparent, sudden, unexplained disaster on one of the country's most important railway lines, the question of how has to be asked. Soon after the tragedy, investigators were dispatched to the site to pick over the wreckage and the collapsed bridge. Upon seeing the locations of the carriages and the missing span of the bridge, investigators concluded that the 22 foot failed steel girder span must have failed before the train had begun its passage on the bridge, thus hinting at something other than the train itself causing the collapse. The bridge had the top portion of pier number two broken off, and this was lying under the bridge between piers one and two. Pier number three was smashed above the base into at least four pieces and pier four was completely missing, having broken into multiple pieces itself. Piers one, six, seven and eight were not damaged, but what was the cause of the dramatic damage to the piers? Well, investigators looked into the bridge's past and pointed to the likely cause to be further upstream at the Crater Lake. You see, the beginnings of the 1953 disaster goes all the way back to March 1945 and Mount Ruapeu's eruption. The debris from this formed a naturally occurring Tephora dam at the Crater Lake, which in turn caused it to fill with water. Eventually, this dam would be insufficient to hold back the lake, and sadly, the tipping point was the 24th December 1953. This was channeled down the Huangyu River, carrying with it a high content of ash deposited from the 1945 eruption. This torrent of effluent smashed into the previously weakened bridge, causing pier four to fail, sending the span into the river. The investigators had to deal with the questions on the bridge's original design, suitability, but an earlier fire at government buildings before the disaster had destroyed the plans. But what we do know is the bridge wasn't suitable or was seriously weakened enough for this particular lahar. The disaster would improve the safety in the area, as the New Zealand Railways Department will install a lahar warning system upstream to alert train control to high river flows. The passerby who alerted the train, Cyril Ellis and passenger John Holman, were awarded the George Cross for a bravery that day. And God, English and passing traveller Arthur Dua Bell both received the British Empire Medal for their actions that saved 15 lives. Sadly, the disaster was a pure accident of bad luck. Although the bridge was likely deficient, if the train was early or really delayed, the tragic loss of such life might not have happened. The bridge would be rebuilt, reconnecting the vital railway line for the country. So the disaster I'm going to rate here seven on my scale and also seven on my legacy scale. Do you agree? Let me know in the comments below. This video is a plain difficult production. All videos on the channel are creative commons attribution share alike licensed. Plain difficult videos are produced by me, John, in the currently wet and windy south-eastern corner of 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 hints on 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.