Director General of the House of Commons, Mathew Duncan, external member of the House of Lords Commission, Andy Helliwell, Chief Operating Officer of the House of Lords, Shrinivas Honap, external member of the House of Commons Commission, Nora Senior, external member of the House of Lords Commission, Louise Wilson, external member of the House of Commons Commission. Exterior Sir Charles Barry's collaborative design for the Palace of Westminster uses the Perpendicular Gothic style, which was popular during the 15th century and returned during the Gothic revival of the 19th century. Barry was a classical architect, but he was aided by the Gothic architect Augustus Pugin. Westminster Hall, which was built in the 11th century and survived the fire of 1834, was incorporated in Barry's design. Pugin was displeased with the result of the work, especially with the symmetrical layout designed by Barry; he famously remarked, "All Grecian, sir; Tudor details on a classic body". Stonework In 1839 Charles Barry toured Britain, looking at quarries and buildings, with a committee which included two leading geologists and a stonecarver. They selected Anston, a sand-coloured magnesian limestone quarried in the villages of Anston, South Yorkshire, and Mansfield Woodhouse, Nottinghamshire. Two quarries were chosen from a list of 102, with the majority of the stone coming from the former. A crucial consideration was transportation, achieved on water via the Chesterfield Canal, the North Sea, and the rivers Trent and Thames. Furthermore, Anston was cheaper, and "could be supplied in blocks up to four feet thick and lent itself to elaborate carving". Barry's New Palace of Westminster was rebuilt using the sandy-coloured Anston limestone. However, the stone soon began to decay due to pollution and the poor quality of some of the stone used. Although such defects were clear as early as 1849, nothing was done for the remainder of the 19th century even after much studying. During the 1910s, however, it became clear that some of the stonework had to be replaced. In 1928 it was deemed necessary to use Clipsham stone, a honey-coloured limestone from Rutland, to replace the decayed Anston. The project began in the 1930s but was halted by the outbreak of the Second World War, and completed only during the 1950s. By the 1960s pollution had again begun to take its toll. A stone conservation and restoration programme to the external elevations and towers began in 1981, and ended in