On my monthly search through the online section of the Imperial War Museum's Archives, I noticed something wrongly titled.
They have what they call a MKIV with an experimental hydraulic transmission... and it is clearly a MKII or III. Is this just their mistake or is it a commonly mis-captioned photo?
Looks like they've called them all MKIV hulls... just realised their photo of the MK1 salvage tank has been titled the same. :-s
It's rampant, Helen; http://www.iwm.org.uk/collections/item/object/205249659
Not a "MkIV" in this case, but a MkII that they call a MkI.
I'm afraid life's not long enough to correct everyone else's mistakes. I have enough trouble with my own.Gwyn
According to source: Landships – British Tanks in the First World War (Page 22, 23 Photo, 40), it was a Mark II.