Thiepval 1932 by Battlefield Historian on Flickr.
The Thiepval Memorial, the Memorial to the Missing of the Somme, bears the names of more than 72,000 officers and men of the United Kingdom and South African forces who died in the Somme sector before 20 March 1918 and have no known grave. Over 90% of those commemorated died between July and November 1916. The memorial also serves as an Anglo-French Battle Memorial in recognition of the joint nature of the 1916 offensive and a small cemetery containing equal numbers of Commonwealth and French graves lies at the foot of the memorial.
The memorial, designed by Sir Edwin Lutyens, was built between 1928 and 1932 and unveiled by the Prince of Wales, in the presence of the President of France, on 1 August 1932. (source)