The badge is either Royal Welch Fusiliers, Royal Inniskilling Fusiliers, Royal Munster Fusiliers, or as has already been suggested, Northumberland Fusiliers.
The jacket he is wearing is a standard issue khaki drill fatigue jacket, worn to protect the uniform, or in warmer climes, on its own.
Traction engines were used to pull he big guns in WW1, and it's from these that tanks were developed.
I don't think it is the 60 lb'er that has been suggested, the bits on the side and top are quite different.
Also of note is that he is not wearing puttees.
I would have expected to see part of a funnel if it was an engine, and the piston type bits do look like a large artillery piece. Bu of course one cannot rule out an engine due to the weedy looking wheels which would have been a bit forlorn in supporting a huge gun
Now, why was an infantryman pictured with such an item??? We can't see his collars to see if there is a Labour bn badge there, so was he just on fatigues, just passing and thought it a good photo op, or what???
I must say that there are plenty of pics of me in/with bits of kit that I really shouldn't be with, so any descendants of mine will have a hard time working out what I've been up to!! One of the best ones is full scarlets....with a UN beret!!! And of course the requisite helicopters, tanks, and captured kit!!!