In a special promotion, MasterCard is briefly letting people ride the Transport for London network for free on Mondays so long as they use Apple Pay.
The promotion is running from Nov. 23 through Dec. 14, according to MasterCard. The only condition is that users have to touch in and touch out using their iPhone 6/6s or Apple Watch.
It's not clear whether the promotion is being done independently or at the behest of Apple, especially as both companies benefit from Apple Pay. Each makes money off transactions, with MasterCard also gaining improved security, and Apple keeping people locked into its platforms.
Transport for London operates trains and buses across the city, including the famous London Underground. It was one of the first parties on board with Apple Pay when the service arrived in the U.K. in July.
Last week Apple Pay came to Canada and Australia via American Express. Simultaneously Apple added support for two more U.K. card issuers, TSB and Tesco Bank.