Big Finish’s UNIT audio series has reliably been a cracking listen over its first three boxsets, as it has finally given the alien-busting organisation a show of their own. For the fourth boxset, it is time to pay homage to the past by bringing on board some of the much beloved stars of the original era of UNIT from the 1970s.

UNIT: Assembled opens with Matt Fitton’s ‘Call to Arms’ which sees Sergeant Benton and Mike Yates reunite for a celebration at Benton’s pub – and end up getting caught in the middle of a skirmish with the Silurians. The threat of a worldwide Homo Reptillia insurrection is nicely set up here – with Richard Hope’s Grand Marshal Jastrok at the head – but the real highlight has to be having John Levene and Richard Franklin back in the saddle.

‘Tidal Wave’ by Guy Adams is perhaps the best of the bunch, however. While it’s nice to have the Sea Devils thrown into the mix, its success is mostly due to the inclusion of Katy Manning as Jo Jones. Adams nails the older Jo seen in The Sarah Jane Adventures – a charming yet absent-minded eco crusader – and naturally Manning is as excellent as ever. In particular, her pairing with Osgood is a delight.

Adams also wrote ‘Retrieval’, which switches the focus to the current UNIT team as Kate and Osgood travel to a Silurian base in the Mediterranean. Instead of a 70s legend, the guest star here is Neve McIntosh, the resident Silurian actor on TV. McIntosh offers a great performance, as she gets a chance to reacquaint herself with the sinister side of the species after playing the loveable Madame Vastra for the past few years.

‘United’ by Matt Fitton draws the disparate threads of the series together with aplomb, with all four guest cast members returning as the Silurians and Sea Devils lay siege to Great Britain. Hats off to the ambition of Fitton’s script here, as you can easily imagine this as one of those global-scale TV episodes (see: ‘The Zygon Invasion’). What’s more, Fitton keeps all the elements in check, with each of the characters getting a shot in the limelight.

All in all, UNIT: Assembled might just be one of the best examples of Big Finish blending the worlds of classic and modern Who together, as it combines some welcome homages to the past as well as marrying it with the scope and style of the contemporary stories. Comprised of four thoroughly entertaining adventures, this boxset is a treat for Doctor Who fans of any age.

UNIT – ASSEMBLED (DOCTOR WHO) / DIRECTOR: KEN BENTLEY / WRITERS: MATT FITTON, GUY ADAMS / STARRING: JEMMA REDGRAVE, INGRID OLIVER, JAMES JOYCE, WARREN BROWN, RICHARD FRANKLIN, JOHN LEVENE, KATY MANNING / PUBLISHER: BIG FINISH / RELEASE DATE: OUT NOW