 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 splendor. 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 external and internal stonework. Sound-colored limestone from Yorkshire was used to build the Palace of Westminster because it was ideal for elaborate carving. But owing to its inherent qualities, combined with the effect of hurried delivery from the quarry and poor practice in some of the workmanship, the stone decayed in the London atmosphere of the time. And because the city's air quality is still poor, albeit due to a different modern-day pollution, this decay and damage is still going on. Although these defects were visible as early as 1849, before construction of the palace was even completed, very little was done to prevent its decline during the 19th century. Work was carried out in the 1980s on outward-facing elevations and in the 90s to some internal courtyards. But there is still a huge amount of essential work to be done. This is one of the inner courtyards which didn't benefit from the conservation work carried out in the 80s and 90s to the more public-facing courtyards. It's had another 30 years of damage caused by sulphurous pollution and the damage will escalate. You can see that from the days when there was a lot of sulphur in the atmosphere, it's blackened. The longer this pollution is allowed to stay there, the worse the damage gets and it's still eating into the face of the stone now. This is a really good example of a build-up of this sulphurous pollution. Once we can get rid of this throughout the Palace of Westminster, our stone will be safer. The problem we have with the stone is that it wasn't left to case-harden as stone should be when it comes from the quarry. In addition, much of the stone has been bed-faced. Correctly, it should be laid that way up. It should not be laid in the other direction. So we have stone very susceptible to damage. If you look higher up, you can see where they've had to take off a couple of the coping stones for safety reasons because they became so precarious somebody was going to get injured. And you can see the gargoyles up at the top there. They still carry a lot of carbon deposit underneath them. There again, this is eating away at the surface of the stone. If we don't do something about these very soon, we'll lose them all together. This is the east elevation of Westminster Hall. This is an area which has never been cleaned or repaired and you can see quite clearly what's beginning to happen here. As I brush my hand across it, the whole surface is coming off and this is corrosion caused by the carbon deposits on the surface of the stone and the combination of that and the rain. And you can see further up here exactly where all the surface is delaminating. And if we don't actually treat this soon, large pieces of stone will start to fall off and it becomes completely irreversible. And in that situation, we lose major parts of the historical value and the heritage of the building itself. The original linings to the palace are Painswick stone from Gloucestershire and Caen stone from France. They were both easy to work and ideal for carving into the iconic images around the palace. But today, much of it is dirty and suffering from wear and tear or damage. We're in member's entrance, which is a fantastically finely carved stone area and directly above this is a location for rather large toilet installation. And you can see just above me here is water staining on the stonework. The water is coming from pipes hidden away in the ductwork in the toilets, which are also directly above this area. The water has to soak through the rubble in the vaulting above me before it actually shows on the surface of the stonework. Ultimately, we're going to lose all this decorative stonework up here and you can see it's extremely fine carved work. It's going to be very difficult to repair and certainly we won't be able just to patch it in. The loss of this stonework, of course, has two repercussions. One is, of course, as you can see, the decorative nature of it but the other point is that the bits of stone will start to fall off and we've already had this problem in a number of other areas in the palace where water penetration has caused salt migration and pieces simply fall off. While longer term plans for the restoration and renewal of the palace are being considered the programme of conservation and repairs of the stonework at highest risk of irreversible damage and decay continues but much of the required work isn't being done because it can't be accessed easily and the disruption it would cause during sittings of parliament. To find out more, please watch the other videos in this series.