I have just come across a Flickr photostream with very good quality images of this tank, and noticed for the first time the words 'Exeter August 1954' (with some letters before it I can't make out) written in what looks like weld lines (?) on the cab roof hatch.
Can't help with the significance, but I think Exeter is someone's name rather than the place - C. H. Exeter. Where was the tank in 1954?
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"Sometimes things that are not true are included in Wikipedia. While at first glance that may appear like a very great problem for Wikipedia, in reality is it not. In fact, it's a good thing." - Wikipedia.
Well according to Bovington the tank was at Bovington from 1949... so I would say as James suggests its a name, that perhaps its someone who did some work on the tank in 1954....
Grateful for your advice regarding modifications made to the original Mark I design for the Mark II training tank, in particular the engine silencer / exhaust system and location of the fuel tanks.
Most images of mark IIs in France shown the original Mark I exhaust outlet yet interior pictures of 785 at the Tank Museum show some form of silencer and a fuel pipe feeder system.