If you think triathlons are for wimps and the Three Peaks have peaked, this 10-12-mile run with 20-25 military-style obstacles designed by the British Special Forces may be just the endurance challenge you seek. Unusually, a number of the obstacles can't be completed solo, making this as much a teamwork challenge as a race, and participants have to battle all manner of obstacles, including fire, ice, water, electricity and yes, mud. Lots of it. And you don't even get a medal for completing the course – how hardcore is that? If this sounds like your kind of thing, you'll be pleased to know there are two separate events for north and south London, so register, get training, and get stuck in. You can choose your start time when you register, and registration closes on April 26.