Landships II

The photo looks like the one from Jones, Rary, & Icks. It is a Mk V, modified by Fowler's of Leeds, where iirc Lt Col Philip (or Phillip) Johnson had worked at some point.

The previous answers are correct: it is a Mk V used to test P Johnson's wire-rope articulated track, often called "snake track", although some sources suggest that term should really apply to the track of the Light Infantry Tank, which was intended to curve in fast turns.

If memory serves, the serial number is 9425 - there's a side photo on Wikipedia (commons, probably). This vehicle was apparently capable of higher speed than 12mph, which was apparently the speed of a different Mk V modification with a V12 engine and no suspension (ouch!). Performance was close to 20mph for this particular snake-track Mk V, as I understand it, and the tank was demonstrated before officials at Roundhay Park in Leeds in May 1919. Military Modelling magazine (March '71) describes this event, but says it was the Medium D itself that was shown that day.

As for Johnson, James is right, he did work for Fowler's: he apparently joined the company in 1902 and left in 1916 when he took a commission in the Army. His path soon crossed with that of the tanks. Late-on and after the war, Fowler's were sent this Mk V which was lightened by stripping out unnecessary panels, etc, then built three or four of the five/six Medium D prototypes (the original design).

Here are a couple of pics on Wikipedia:

side

quarter

PS - although it looks similar, the Tropical Tank apparently only had the wire-rope suspension - the tracks were conventional; the flexible/articulated tracks appeared on the Medium D series, the Johnson Light Infantry Tank, and the American M1922 Medium A.