submitted to Parliament. Ayrton Light A new feature was added in 1873 by Acton Smee Ayrton, then First Commissioner of Works and Public Buildings. The Ayrton Light is a lantern sited above the belfry and is lit whenever the House of Commons sits after dark. It can be seen from across London. Originally, it shone towards Buckingham Palace so Queen Victoria could look out of a window and see when the Commons were at work. Clock Dials Augustus Pugin drew inspiration from the clockmaker Benjamin Lewis Vulliamy when he designed the dials. Each is made of cast iron sections bolted together. The whole frame is in diameter making them the third largest in the UK. They each contain 324 pieces of opalescent glass. Originally, the dials were backlit using gas lamps, at first only when Parliament was sitting, but they have routinely been illuminated from dusk until dawn since 1876. Electric bulbs were installed at the beginning of the 20th century. The ornate surrounds of the dials are gilded. At the base of each dial is the Latin inscription , which means "O Lord, keep safe our Queen Victoria the First". Unlike many Roman numeral clock dials, which show the "4" position as IIII, the Great Clock faces depict "4" as IV. The clock's gun metal hour hands and copper minute hands are and long respectively. When completed, the frame and hands were Prussian blue, but were painted black in the 1930s to disguise the effects of air pollution. The original colour scheme was reinstated during the 2017–2021 conservation work. It was found that no fewer than six different colour schemes had been used over the past 160 years. The Victorian glass was also removed and replaced with faithful reproductions made in Germany by glassmakers Glasfabrik Lamberts. Movement The clock's movement is known for its reliability. The designers were the lawyer and amateur horologist Edmund Beckett Denison, and George Airy, the Astronomer Royal. Construction was entrusted to clockmaker Edward John Dent; after his death in 1853 his stepson Frederick Dent completed the work, in 1854. As the tower was not completed until 1859, Denison had time to experiment: instead of using a deadbeat escapement and remontoire as originally designed, he invented a double three-legged gravity escapement, which provides the best separation between pendulum and clock mechanism, thus mitigating the effects of rain, wind and snow on the dials. Dent never