London's transport network has now seen more than one billion fares paid through contactless payment cards, according to a press release from Transport for London.

Of these, almost one in 10 contactless transactions are now made using mobile devices, with more than 31 million journeys made specifically using mobile phones in London in the last 12 months.

The landmark figures, which the transit agency published this past week, show that, on average, two million journeys are now made using contactless every day.

In total, 40 percent of all pay-as-you-go journeys are now made using contactless. This is up from 25 percent in early 2016.

"London continues to lead the way in terms of contactless payment around the world, and the money we make selling TfL's innovation and expertise to other major global cities will allow us to put further money into improving London's own transport network," Sadiq Khan, London's mayor, said in the release.

The agency's contactless payment system was first launched on London's buses in December 2012 and expanded to cover Tube and rail services in London in September 2014.

The system automatically calculates the best value fare based on the customer's specific journey history and then charges them at the end of the day, ensuring they always pay the lowest fare in the easiest and most convenient way, according to the release.