A Freedom of Information Act request by The Guardian shows 39,560 ads were shown across the capital's buses and trains between April and September 2021.
They included promotions for exchanges including eToro, Crypto.com and Luno — alongside billboards promoting the Floki Inu memecoin.
Some of these ads ended up getting banned by the U.K. Advertising Standards Authority, and affected companies were told the billboards couldn't appear in the same form again.
Perhaps more concerning for regulators will be the appearance of ads for advanced products such as trading bots, which are designed to automate the process.
Transport for London has said that it vets all ads before they are allowed to appear on its services — and the newspaper reports that promotions don't run if they feature similar language to those seen in banned ads.
Should Crypto Ads Be Banned?
Politicians in the city have previously urged Transport for London to ban cryptocurrency advertising altogether.
Critics have argued that many ads trivialize investing life-changing sums of money, and fail to make clear how volatile digital assets can be. Others compare the act of trading cryptocurrencies to gambling.
But with passenger fares tumbling substantially as a result of the coronavirus pandemic, TfL has been confronted with a significant black hole in its finances.
Crypto companies — not just in the U.K., but around the world — have expressed exasperation at the lack of clarity provided by regulators. Some have also accused advertising bodies of censorship, and argue that they shouldn't be treated any differently to platforms focused on traditional assets.