Yes Richard - a bad workman blames his tools.
If that's what caused it, that's a lesson for me that's for sure. Although, if I may say to the court - I took my time with this and made sure the socket was down hard and square on - but clearly - I haven't mastered that adapter. In putting the plug back in I used a Sidchrome plug socket with a rubber inside - the Kinchrome was plastic, (go figure) - and the Sidchrome sat well - I used an extender bar from the socket set that had a square-shanked nut-type end on the shaft and a conventional crescent type spanner to nip it up. I'll be doing that in for No.2 plug in future that's for sure.
and Ryan - I like the .410 Lee Enfield idea!!!! Got me thinking...