Hutch,
Is that earth pin on the Crabtree plug like the one that's been adopted on 15A plugs in the RSA?
On the 110V BS plug issue, I don't know if there ever was a British Standard plug for the lower voltage. I know that in the very early days (e.g. 1890s) some towns set up 3-wire DC Edison systems running at 110/220 (or thereabouts), but I believe they were all changed to the higher voltages very soon afterward, probably as 200-250V bulbs became available.
It would be interesting to find out just when the last 110/220 supply was converted, but I think it was very early on.
