 The Palace of Westminster is home to one of the busiest parliamentary institutions in the world. Thousands of people work here and visit every day. And millions of tourists are drawn to its iconic splendour. Completed in the mid-1800s, many of the palace's features have never undergone major renovation. So what's being done to tackle any problems? Not only to ensure the palace continues to function as a working building, but also to preserve its unique heritage for future generations. In this video, we will look at the palace roofs, towers and rainwater drainage system. When these cast iron-tiled roofs were installed on wrought iron structures in the mid-1800s, it was cutting-edge technology built to last. But now, 160 years on, the roofs are in fact leaking, bringing significant damage to the stonework, fabric and historic interiors of the building. The palace has some of the most valuable Victorian interiors in the country. If nothing is done about repairing the roofs, there is a risk of severe damage, if not total loss to some of these interiors. This now needs to be addressed urgently. So a phased programme of roof repairs and replacement is already underway to ensure the building is watertight before any major restoration and renewal work inside begins. It's now come to the stage where it needs major attention. And if you just look behind me, you can see where there's been water ingress. You can see the result of rust and salts, the capillary attraction where the mastic has gone in between the trusses. You can see that temporary spaces have had to be put in to ensure that the roof tiles don't actually fall apart. This is the back end of the gutter and you can see especially along the top of the gutter flashing here where there's been water ingress and the severe rusting. Gradually, these things are taking hold. Water ingress is increasing and bits of it are quite literally falling off. Repairing the roofs is a major logistical undertaking. There's a huge amount of scaffolding that has to be put up in order to erect a gantry of sufficient strength to move the tiles. This whole procedure is quite noisy and we're limited to the noisy works when the houses are not sitting. Each of these, as you can see, is very large. It's 750 square, about 15 millimetres thick. Each one weighs 75 kilos, has to be gently lowered to the ground to be basically sandblasted, assessed for condition, and at that point we find out just what needs to be done to them. Some tiles cannot be rescued and we simply have to recast them. And the technology of casting a cast iron slab that thin is quite complex. This is the result of phase one where it's been completely refurbished and it looks absolutely fantastic, exactly as it should be and probably even better than it did in the beginning. We've also managed to rationalise the fire escapes across the roof and the access to it. After all this work, we think it will last well in excess of 100 years. We're now about to start phase two of the cast iron roof works which will go on for several years yet, we think another eight or ten years. Cloister Court, hidden in the centre of the building, is one of London's lost sites and one of the few surviving parts of the old palace, originating from the 14th century. A lot of work needs to be done here. This particular roof is a replacement, is a post-Second World War replacement, there was severe war damage to this and it's a concrete slab with mastic asphalt on top of that and concrete tiles on top of that. And this has turned out to be practically impossible to maintain. There are plants growing out of the mastic asphalt and this brings a leak of course. The water runs underneath the concrete, underneath the asphalt and drops in in all sorts of places and you can't actually trace where it's coming from. What ideally needs to happen is that this concrete slab is removed and we reinstate the original double pitched slate roof in the middle with wide gutters at the side and that would enable us to ensure that it remains waterproof and to maintain it properly. There are a number of towers gracing the silhouette of the Palace of Westminster many of which are made of cast iron and this is Jay Tower and you can see where we've had to put in temporary bracing on the pinnacles on the corner which have suffered from rust-jacking and were actually about to fall off. Each of these pinnacles weighs probably in excess of 75 kilos and would cause a great deal of damage if it were to fall off. Rainwater runs along guttering into hoppers and through downpipes. Most of this cast iron system is from when the Palace was built. Some of the piping disappears into stonework to ensure the integrity of the architecture but over the years it's rusted and sprung hundreds of leaks causing a multitude of problems to nearby windows and interior stonework. Temporary repairs are being carried out to the guttering and downpipes but because of the decay and rust the only real solution is to replace them. This is underway but much of it is hard to access meaning the rate of repair and replacement is very slow. However limited this approach must continue until a longer term plan for the Palace's restoration and renewal is agreed. To find out more please watch the other videos in this series.