 The building had been faced with mosaic tiles, but these were impossible to repair and were replaced with glass-reinforced plastic, which gave it a thicker appearance.The aluminium in the lantern was replaced by stainless steel, and the slate paving of the platform was replaced with concrete flags.The crypt under Liverpool Metropolitan Cathedral is the only part that was built according to Lutyens' design before construction stopped due to World War II; in 1962 Frederick Gibberd's design was built upon the Lutyens crypt.