These four pictures came together but they may not originally have been together and could cover any period of time.
The line Of WM20s is of that intersting but anoying period when the census numbers were only on the other side of the tank, and what are those two Armoured vehicles behind them?
The DXL registration on the Sunbeam dates from 1937.
I suspect that the M20s have the serial on the front number plate blade.
As far as I can tell from Vehicle Markings 1941, "41" on blue-white is likely to indicate the signals section of a reconaissance battalion. Does that give any clue to the odd armour behind ?