Most expensive potential mistake I made was with a teacher taking a group from one of the stations on the Severn Beach line to Bath. Something like 8 adults and 56 children and he wanted them as normal individual fares. He came to the booking office fairly late one evening wanting them for the following day. I rattled them through APTIS. He paid by credit card. I look down at the pile on the turntable as I am about to spin it and realise I had omitted to change the date. Refund to card. Issue them all again with the correct date and a long session of non issues and summoned to the supervisors' office the following day.
