The 33-year-old intends to complete the London Marathon on Sunday dressed as one of the mischievous Irish sprites, complete with beard and stripy tights.
However, just being in fancy dress isn't enough - Tom also wants to win a Guinness World Record for being the fastest leprechaun to ever complete the daunting 26.2 miles.
We weren't even aware that there is so much competition among leprechauns, but we've been reliably informed that the speediest one so far reached the finish line in four hours and 22 minutes.
Tom's doing it all for charity the Sailors' Society, so give him a wave if you spot him!
"I am hoping that running as a Leprechaun will help me raise a pot of gold for them so they can carry on their good work," he enthused.
And while you're at it, keep an eye out for Tonya Hills from Bansted who, according to the Sutton Guardian, is running the same race dressed as a nurse to raise money for the Royal Marsden Cancer Campaign.
If you're in need of a costume for the marathon, there's still time! Use You can run as anything you like, including a leprechaun or a nurse, so let your imagination run wild!