The hack involves submerging the card into acetone in order to remove the chip and antenna. Once removed, the chip and antenna are embedded in a resin ring.
I'm assuming it will be a bit difficult to refill the hacked ring but I'm loving the exploration of using alternative objects other than cards (and mobile phones) for transportation payment.
Sutanto does warn you that hacking into an Oyster card is illegal. Let's hope we don't get him into trouble.