Thanks for sharing Kieron.
The Sherman pictured is an early one, but not one of the very first to arrive in North Africa. This one is a welded hull version probably a diesel engined M4A2 (Sherman III in British parlance), it could however be an M4. Impossible to tell for certain from that angle but not many M4's were delivered to the British. The fact that it is a British vehicle and not an American tank being used for training, can be seen from the unique stowage. The fittings for the sandshields are present as is the framework box for storage of the POW cans on the front fender. It is also possible that the edge of a rear turret storage box can be seen. I'm not sure.
American tanks in the theatre generally remained in their olive drab and were not repainted sand, another British indicator.
It is not one of the very early tanks delivered because it is fitted with the heavy duty bogies, the ones with the trailing return roller rather than the M3 type bogies with the roller positioned centrally above.
It does retain the early features of the direct vision slots on the glacis for the driver and co-driver and the M34 75mm gun mantlet, here fitted with the splash guard for the co-axial .30 cal. I think it has the early three part transmission housing too.
The T48 rubber chevron tracks are also an early feature and probably the ones it was shipped from the States with. In British service these were soon replaced with steel tracks.
So, I would say the photo was taken some time in late 1942 into early '43.
A very interesting shot.