Can't afford black cabs? Look out for one of these fancy cabs on 3 and 4 July.
For two days only, 10 of these cabs will be offering Londoners in zones 1 and 2 free rides.
And there's a message behind the stunt: London is one of the UK's pollution hotspots, and this particular fleet of Barclays Air cabs uses an air cleaning device invented by Airlabs, which removes up to 95% of pollutants, such as nitrogen dioxide (NO2).
Apparently this makes the air in the cab as clean as that found in the Peak District National Park.
If you're thinking it's a bit rich to have a load of petrol-guzzling cabs zooming around, preaching about clean air, the fleet consists entirely of TX zero-emission electric cabs.
How do you get a ride? Just keep an eye out for the white and blue livery. The cabs will be driving around between 8am-8pm on 3 and 4 July. We're told there's 'no limit' to where they'll take you, although your driver might raise an eyebrow if you order them to hotfoot it to Heathrow Terminal 5.
If you don't manage to catch a freebie, the cabs will be around London for another 12 weeks (you'll just have to fork out).