He said the first Ipsa knew about it was when he turned up at the office with a cheque to refund the amount he had been accidentally paid.

BBC: Ipsa must 'raise its game', MPs told

Shashi Verma, TfL's director of customer experience, said: ''Pay as you go Oyster cards do not expire and customers are able to return their cards to a Tube ticket office at any time for a refund of the remaining balance and card deposit.

BBC: Unused Oyster cards valued at ?55m