Apple has been alerting customers in the United Kingdom about this news by email, pointing them to a new page on its website with more details.
Apple has tweaked its Apple Pay service in an effort to reduce queues at London Tube-station barriers.
Under Express Mode, users don't need to authenticate their payment with Face ID or Touch ID but may simply touch their iPhone or Apple Watch on the yellow card reader to proceed with their journey.
The Express Transit feature will work on iPhone SE, 6S and later models as well as the Apple Watch.
More useful, perhaps, for late night travellers in London is that the system doesn't need power to be on and will work up to five hours after the red Power Reserve icon appears, however that particular feature will only work on iPhone XS or Apple Watch Series 4 devices or later. Select a card and then authenticate with Face ID, Touch ID, or your passcode. The downside is that if you leave your phone on one of the afore-unlocked train or bus journeys any random will be able to enjoy free travel, until you get home to your main Apple device and initiate a remote lock and have the Apple satellite detonate it and the thief from orbit.
This feature is available for the public transport services in several other regions, including New York (MTA), Portland (TriMet), Japan (Suica cards) as well as Beijing and Shanghai.
It's the first time Express Transit has been enabled in the United Kingdom, after countries including China and Japan, as well as a trial in NY.