Beneath Waterloo station, at the end of a graffiti blazon stretch you’ll find the Vault Festival – the epitome of underground theatre. Step inside a cavernous treasure trove of makeshift venues and pop-up bars, and you’ll discover that the spirit of the Fringe is alive, well and thriving in SE1. The reason for my visit was to see Fat Man, a modern retelling of the myth of Orpheus. Now a musician and a stand-up comic, Orpheus recounts his tragic tale in the style of a comedy routine to a crowd that is made up of Cupid and Hades (to name but a few of the deities that sat amongst us). With a bulging shirt and a penchant for donuts and liquor, Orpheus (Martin Bonger) is a witty, moving reframing of a Greek myth, that will make the godly pack laugh in parts yet auspiciously moves them to tears in equal measures.

The epic nature of Greek myths can sometimes render them inaccessible, however Fat Man is told in such an engaging manner that it retains all of the emotionally charged sentiment and still manages to be accessible. In a nutshell, Orpheus is the story of a widower who was told by Hades that he would be reunited with his late wife if he crossed the river Styx without ever once looking back. However, resisting the urge to look back at his beloved wife is nigh on impossible, or as Orpheus surmises in his modern day equivalent of trying to eat a donut without licking your lips (a feat that he attempts twice during the show). Fat Man is a heartbreaking lament of a grief-stricken man consumed by regret.

There were clearly a few classics students in the audience as chuckles reverberated around the room at some of the more obscure Greek references. Although much of Orpheus’s comedy material relies on at least a basic understanding of myths of that ilk, the overall play does not. Some of the comedic material felt a little safe and vacuous. Personally I thought that Fat Man really found its stride when Bonger conveyed raw undiluted emotion: for instance, the moment when he tries to reach out and touch his wife’s shadow and it just evaporates from sight. You can’t help but feel moved by the vulnerability of a broken and dejected man.

Bonger’s performance as Orpheus is faultless. An entrancing and hypnotic soundscape was provided by Philippe Nash, coupled with an ethereal lighting display, and matched perfectly by the dynastic and decrypted setting provided by The Vaults. With a running time of just an hour, Fat Man really packs an emotional punch. As you leave the troubles of the emotionally bankrupt and broken-hearted Orpheus behind, you’re then thrust back into the hustle and bustle of promoters tirelessly handing out flyers for their shows. The spirit of the Edinburgh Fringe is alive and well in a vault in London’s Waterloo.

Fat Man is playing at the Vault Festival until 15 February. For tickets and more information, see the Vault Festival website.