I think the drive is 1/2", I can't confirm this as I'm away from home at the moment and won't be back for 2 months. Any information at the moment is a great start.
Can anyone help me with this tool, it's a Wakefield No 26... July 1921?
The end that's circled is hexagonal to accept the extension pieces and sockets.
The action of the tool is the baffling part, if I new what it was for then the action may be answered.