Actually, @tomscott is wrong with this one:
You want #IEC60906-1 and not #BS1363 connectors because they are evidently superior on all cases...
https://www.youtube.com/watch?v=UEfP1OKKz_Q
https://en.wikipedia.org/wiki/IEC_60906-1
https://en.wikipedia.org/wiki/BS_1363

