BBC Radio 1 presenter Nick is challenged to cycle for 12 hours in a bid to cover 1000 miles, in the hope of raising as much money as possible for this year's Sport Relief campaign.
Having started the cycle at 7am this morning, Nick is hoping to finish his challenge at 7pm this evening.
As he started his cycle, 29-year-old Nick wore a black jumper emblazoned with the words 'surfboard', which is a reference to Beyoncé's 'Drunk In Love' single with husband Jay Z.
He later changed into the official Sport Relief T-Shirt as he made a hand gesture to photographers!
The tough challenge is taking place in a transparent box outside the BBC Broadcasting House and Nick has been joined by his fellow BBC DJs, plus a host of showbiz pals from the worlds of music, TV and sport.
Sport stars Victoria Pendleton, Amir Khan and Ben Foden helped to rack up miles this morning towards the grand total.
Davina McCall, who completed her gruelling Sport Relief challenge last month after swimming, cycling and running a combined total of 500 miles, also showed up to give Nick some words of motivation.
Getting on the bikes for a 30 minute stint was soap stars Ashley Taylor Dawson, Verity Rushworth and Danny Dyer.
Meanwhile, former TOWIE star Lydia Bright also joined in on the sporting activity. Lydia posted a video to Instagram earlier today, in which she was cycling with Ollie Locke and X Factor star Nicholas McDonald.
Captioning the video, the fashion designer said: "Not your average Monday #GoGrimmy #SportRelief2014."
It doesn't look like Nick's close friend, One Direction star Harry Styles will be able to make it down, but he did tweet his support earlier today and gave fans a link to the sponsorship page.
Nick's friends have also been feeding him well, and Pixie Geldof turned up to give him some sugar supplies. The 23-year-old was pictured clutching onto a can of Diet Coke and a packet of Jelly Babies!
Also getting in on the action was McBusted, Ferne Cotton, Professor Green, Daisy Lowe, Wretch 32 and N-Dubz star Richard Rawson - aka Fazer.
More celebrities are continuing to pop down and show their support - Nick really does have a lot of showbiz friends!
Nick's challenge is part of the wider BBC Radio Around the World challenge for Sport Relief, in which the whole of BBC Radio is attempting to run, swim and cycle 25,000 miles, which is the circumference of the world.
To sponsor Nick, click here.