May be I should have let the brakes cool down before applying the handbrake or the pads weren't secured properly or the caliper seized, not sure which.
Just took the wheel off to fit new pads with new fitting kit, following the excellent FAQ on here.
I can't get the piston back in, have tried rotating it but it's not budging. Could be that I haven't got anything the right size that is strong enough, I now have a few mishapen metal objects that I tried with.
Any suggestions on: what caused it, is the caliper kaput, do I need to find something stronger to try rotating piston back in before resorting to visiting a local garage?