Landships II

I think this is new. Several 1914 - 18 journals have been put on the Internet: http://www.illustratedfirstworldwar.com/

Including the Illustrated London News. This is their coverage of the offensive at Cambrai: http://www.illustratedfirstworldwar.com/item/the-best-kept-secret-of-the-war-british-tanks-like-those-that-iln0-1917-1201-0005-001/  (N.B. You have to click on "Web Version) Now we can see how all the dodgy i.d. came from.

Nonetheless, an excellent site.

Incidentally, the captions in the IWM collection are all over the place. For example, The photo of C26 is described as "A British tank, probably a Mark III tank, crossing a trench on its way to take part in the Battle of Cambrai, November 1917."