Try key in, turn it as far as you can and then knock the lock on the ground/pole/bike etc.
I used to have a u lock that jammed up every so often and this worked.
@M_V started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
Try key in, turn it as far as you can and then knock the lock on the ground/pole/bike etc.
I used to have a u lock that jammed up every so often and this worked.