The number 38 is one of London's most famous buses - this year the route will have been running for one hundred years. To celebrate this transportabulous event, bus operator Arriva London is teaming up with Maggie's Cancer Caring Centres in an effort to help raise cash for Londoners affected by the disease.
Simply sign up here, pay a £10 registration fee, get some sponsors and slip into your walking shoes. Start at Clapton Pond and make your way along the 38's 7.5-mile route all the way to Victoria happy in the knowledge that the blisters you may well work up are all for a good cause.
The challenge runs from now until the 14th of September, so pick a day and go along with friends, family, colleagues, or simply by yourself. The website of the event even suggests doing it in fancy dress, or backwards - it's entirely up to you.
Each person needs to raise a minimum of £38. Not only is this the number of the bus route along which you'll be walking, but it's also how much it costs Maggie's each time a person visits one of its centres for help.
For your registration fee, you'll receive a fundraising pack, a special T-shirt and lots of advice on how to reach your fundraising target.
Getting in on the act, too, is Krispy Kreme - in the fundraising pack you'll find a voucher for one of the doughnut company's Original Glazed Doughnuts (with the purchase of any medium coffee). You can redeem this at their Victoria station outlet - where the route finishes. Perfect.
If you're interested in making a few stop-offs along the walk, be sure to check out this page, which details a few places of interest along the number 38's route.
Also, if you have any energy left once you get to Victoria, you might want to visit this place, or possibly this one. Or just kick back and get a pint to quench your thirst here.