‘The Palace of Westminster, instead of being ablaze with lights on the river-front, its numerous windows casting their bright reflections on the waters, as in peace-time, is now a vague, shadowy mass even in the moonlight.’
This is how Michael Macdonagh, the parliamentary correspondent of the Times during the war, described the view of the Palace at night in December 1917 (in his book In London During the Great War).
The current Palace of Westminster was built in the 1840s and 1850s, following the fire of 1834 that destroyed most of the old Palace. Its outline is clearly the same today as it was in the Great War. The big difference is the light. Streetlights were kept to a minimum during the war and external lights on shops and public buildings were banned. This has a big impact on the Palace of Westminster, turning it into a shadow at night. Most noticeably, the clock face is dark. In addition the Ayrton Light did not shine. (This is the light at the top of the clock tower that is lit whenever Parliament is sitting after dark, to tell the nation that its elected representatives or the Lords are still at work). In place of those lights are the searchlights, scouring the sky in search of Zeppelins and German aeroplanes. The war also changed the sounds of Westminster, as Big Ben fell silent in October 1914 and did not toll again until November 1918.
The impact of the Great War, though, was much less than the Second World War and the Blitz,as this page at West End at War demonstrates.