Further advice...................the lock would have worn because of constant use on one side only, the other side would be like new and the key would have operated the lock mechanism.
It's a bathroom door Astra. Happened to me twice in two different houses - thankfully not the victim in either case. I replace more dodgy bathroom locks for clients than any other type. They're generally poorly made and frequently used - a recipe for trouble.
Just enlarged the picture.................BIG WHOOPS! phhhhttttttttt.......stuff the lock....get a crowbar! I'm finished with specsavers.