My wife wanted to try SPD's, so I duly changed her pedals and fitted the cleats to her shoes. Only when she couldn't unclip wobbling towards a junction, followed by an emergency trip to
Evans, did it transpire I had fitted the cleat on one shoe the wrong way up. The side that has a countersunk section for the bolts was facing the sole of the shoe, meaning the cleat became locked and needed wrenching off the pedal. Whoops...