A friend was feeling down and I was away the coming weekend to visit another friend and invited her (they are also friends). I got the train tickets and she cancelled in the morning.
So a journey that should have cost me £25, actually cost me £50. She said she would pay me back.
I've now asked for it back (4 weeks later) and she seems to be quite offended.
Just to point out, she knew I was buying the train tickets.