From 16 September 2014, users of the London Underground network in the UK will be able to use contactless payment cards to pay for travel as well as the existing pre-paid Oyster cards. This includes travel on all Tube, DLR and Overground trains.
They will work in exactly the same way as the current Oyster card system, where users simply hold their card next to the yellow receiver positioned at station entrances.
The use of contactless cards for London Underground services has been piloted by 3,000 customers, and follows their use on London buses which began in December 2012.
However, users are being advised to be vigilant in ensuring only one card touches the card reader so that double payments do not occur e.g. one from their contactless bank card and one from their Oyster card when both cards are carried within a wallet which is then held up to the card reader.
Most UK cards incorporating contactless payment technology will be accepted, as will some cards issued outside of the UK (American Express [AMEX], MasterCard and Visa).
Source: Transport for London, BBC