The Imperial War Museum has a new online exhib on Tanks in WW1.
http://www.iwm.org.uk/history/tanks-in-the-first-world-war#lightbox-object-205087388
Also this link to the IWM Research blog and a posting about Tanks and the Battle of the Ancre in 1917.
http://blogs.iwm.org.uk/research/2012/11/restoring-the-first-world-war-film-the-battle-of-the-ancre-and-advance-of-the-tanks-1917/
Both well worth having a look at!
