The Doctor, with Romana in tow, accidentally materialises the TARDIS underground in the opening of Subterranea, the latest Fourth Doctor audio play from Big Finish. But this doesn’t mean they’re far from civilisation – this planet’s mole-like inhabitants live in huge vehicles called Drill-towns, which constantly mine their way around the rocks, picking up resources in order to survive. But there’s another race among the rocks; the cyborgs known as Silex are on the prowl and have a habit of feeding on the Drill-towns.

The story, from veteran Who writer Jonathan Morris, plays out simply but enjoyably, well fitted to the hour-long format and to the era of Who in which it’s set. There are some nice twists, particularly at the end of part one cliffhanger, and the Silex are effectively threatening villains, if at times overly reminiscent of the Cybermen. Perhaps a name not starting with the ‘cy’ sound would have helped.

What makes Subterranea well worth a listen, though, is not the plot but the characterisation of the race who live on this planet. There’s an Industrial Revolution-esque style to them, which makes the whole thing feel like a Dickens novel crossed with Journey to the Centre of the Earth. Matthew Cottle gives a particularly amusing performance as Drill-town Captain Maxwell Wilberforce Bell, who acts like a proud yet petty Victorian factory owner, and Abigail McKern is equally entertaining as his wife Lucretia. They both give their characters comedically over the top Northern accents, and why not – after all, lots of planets have a North! To complete the Dickensian stylings, there’s a sub-plot about an orphaned thief.

It should go without saying that Tom Baker’s Doctor feels right at home bouncing off of all this silliness, but let’s not forget Lalla Ward’s Romana, whose scientific cynicism offers a counterpoint which only amps up the fun. No K9 this time round, however – he’s keeping himself busy in the TARDIS.

So, like most Big Finish audios, Subterranea is a faithful and well-produced addition to a classic era of Doctor Who, and like the best ones, it finds a way to elevate itself from a generic Who story into something a little special – in this case, the sheer whimsy of mole aliens playing at Dickens. Set aside an hour for this, and fun is guaranteed.

DOCTOR WHO – SUBTERRANEA / AUTHOR: JONATHAN MORRIS / DIRECTOR: NICHOLAS BRIGGS / STARRING: TOM BAKER, LALLA WARD, MATTHEW COTTLE, ABIGAIL MCKERN / RELEASE DATE: OUT NOW