Heads up --
TfL -- https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets-and-oyster/buying-tickets-and-oyster?intcmp=54759
"If you got your Oyster card before 23 February 2020, you can get your £5 refunded when you don't need your card anymore. If you got your Oyster card on or after this date, you can get your £5 refunded once you've used it for one year."
More in depth explanation -- https://www.oyster-rail.org.uk/2020/02/bye-bye-oyster-deposit/#more-2731
"TfL are phasing out the Oyster card deposit from February 23rd. Cards purchased before that date will still retain the £5 deposit which can be cashed in when returning or cancelling the Oyster card. From Sunday 23rd onwards an Oyster card will cost a £5 fee. If the card is retained then that £5 will be added to the PAYG credit balance on the first anniversary of purchase. Unused credit will still be refundable at any time, along with the deposit on older cards."