hope this dosen't go over a topic already covered. I was wondering were the rails mounted on the top of british tanks a standard issue item right off the assembly line or were these a field modification if so how common were they ,any info on these would be helpful,thanks
If the rails you're referring to are the rails for the unditching beam fitted to the Mk. IV and V, they were fitted very shortly after construction. There are some photos that show them without rails but usually these tanks are newly constructed.The earlier Mk's weren't equipped with unditching rails but relied on spuds and track torpedoes to get out of shell holes. It is possible that a few earlier Mk's were refitted with rails as the Mk. II at Bovington does have mounts for unditching rails but there would not have been very many because by the time the Mk. IV's appeared in numbers, there weren't very many early Mk's in running condition.
The tanks that were used at Gaza do have a variety of roof modifications for holding stores on top and at least one photo of "Sir Archibald" shows it on the move with the trestles for removing/attaching the sponsons still mounted on the roof.
And here's a photo of Sir Archibald. There's also a good illustration of this vehicle in Osprey's New Vanguard nr 100 on the MK-1 in color, showing this roof contrapsion.
If the rails you're referring to are the rails for the unditching beam fitted to the Mk. IV and V, they were fitted very shortly after construction. There are some photos that show them without rails but usually these tanks are newly constructed.
None of the tanks I've seen photographed on railway wagons in Britain have rails. There are quite a few shots of tanks on wagons in France that have rails and even , in some cases, fascines and cribs. Loading gauge restrictions on tanks in transport in Britain proved particularly onorus right up until late 1942 (and were in fact a restriction of tank design that restricted the turret ring diameter and hence the size if gun fitted). If such problems restricted the the fitting of rails this might have been done in France at Central Workshops or even in the field. This would explain the arrival of War Baby 2 in Egypt sans rails.