This story kicks off a run of fourth Doctor stories from Big Finish, returning to the now familiar theme of Leela’s Pygmalion-esque education, albeit with a savage twist. Written by John Dorney, The King of Sontar is a compact two-parter which maintains a cracking pace throughout. It borrows from the best of Doctor Who whilst still creating something that feels both fresh and dramatically vibrant. Among its partial precedents are Genesis of the Daleks, with this template especially visible at the story's beginning, given that the TARDIS is hijacked by the Time Lords and sent on a specific mission. And certain events also put me somewhat in mind of The Silurians, albeit with less moral clarity in this instance.

Diverted to Dowcra, a lump of rock with strategic importance, the Doctor and Leela soon encounter a Sontaran seemingly unlike any other. This is Strang, played very effectively by Dan Starkey, who evidently relishes the chance to portray a darker and far more deadly Sontaran incarnation than that of his recurring TV role. Strang's introduction here, effortlessly taking on a twelve-strong assassination squad, is certainly a stylish statement of intent, and the character challenges pretty much everything that listeners (and the Doctor) think that they know about Sontarans. Amongst other things, this gives rise to an impressive cliffhanger and a sense of mystery that's resolved perhaps a little too soon. I would have welcomed slightly fewer definitive answers regarding Strang’s origins – he seems too good a narrative possibility to be explained away so rapidly. But there’s little sense of a series-long arc being seeded here, and instead this feels far more like a stand-alone opener. Transformatively reinventing a major Doctor Who monster is surely a strong enough idea to sustain a number of stories, though, and on that basis I partly wish Strang had remained more of an enigma for now.

Leela and the Doctor are separated early on in the proceedings, but Dorney makes good use of this common pattern by partnering Leela with Vilhol, a Sontaran wishing to restore his forfeited sense of militaristic honour. Well played by Big Finish regular John Banks, Vilhol – or “the coward”, as he’s become known – is an intriguing character who comes to recognize Leela as a kindred warrior spirit. It’s a rapidly battle-hardened relationship that in turn raises a curious possibility: perhaps this companion of the Doctor’s might feel more at home with an avenging Sontaran than with a universe-hopping Time Lord? And if that’s so, then whose code of honour will Leela ultimately embrace?

“Why are there always alarms?” mutters the Doctor at one point, and sure enough they continue to blare away in the background across this production, with effective sound design constantly lending a sense of urgency to events. Although a few supporting characters feel hemmed in by archetypal structures – you’re rarely in doubt as to what fates are most likely to befall evil mercenaries and misguided scientists – in the end, this story gives Tom Baker and Louise Jameson some great material to work with. Strang may well represent an unusual Sontaran adversary, but by raising the stakes thanks to a Time Lord mission (and an accompanying threat to the universe), The King of Sontar also moves towards an unusual conclusion for the fourth Doctor and his Sevateem student.

Along the way there’s a lot of fun to be had. Strang and the Doctor confront one another via plenty of strong repartee, and David Collings’ turn as the scientist Rosato is also good value. Rosato has been working on a “portal” which could do away with problems such as galactic famine and over-population, as well as coincidentally making him famous, but unfortunately he has become more than a little blinkered in his technological pursuits. And assigned to help with this development, the Doctor seemingly can’t resist being a clever-clogs. However, it is Strang’s excessive monstrosity that becomes the true star turn. Compelling villains often unbalance the stories that they grace, and Strang is almost akin to a Davros-style equivalent for the Sontaran race: a storytelling development opening up new schisms, identities and possibilities. The analogy is another way in which Dorney’s work here seems to have been productively sparked by remembrance of Genesis.

Previous Big Finish fourth Doctor series have been marred by occasional wobbles in quality, but this is undoubtedly a smartly structured and inventive tale. And with the possible exception of a highly stylized performance when the Doctor's being strangled by Strang, Tom Baker is on top form. The same can be said, without reservation, of Jameson (who effortlessly makes “hatchery” seem like a truly alien word) and Starkey, who revels in Strang's self-belief. As a Sontaran experiment of sorts – whether toying playfully with Vilhol’s last syllable of dialogue or posing questions about the Doctor’s educational skills – this consistently yields first-class results.

Gallifrey V has all the makings of a classic Big Finish drama. Packed to the brim with familiar faces from Doctor Who’s past, this three-episode boxset’s cast ensemble represents a formidable Who’s Who (if you’ll pardon the pun) of talent from the show’s classic and modern incarnations. A well-rounded ensemble, however, is far from a guarantee of a entertainment release’s success (catch last year’s dire sketch comedy Movie 43 and the truth of the matter will become abundantly clear), and in the case of this fifth season of pre-Time War incursions with the Doctor’s race, plenty comes to mind which could (and should) have been altered for the better.

This reviewer can imagine few pre-21st Century fans who would wholeheartedly reject the opportunity of spending further time in the company of Lalla Ward’s Romana or indeed Louise Jameson’s Leela, yet the former companion is cruelly short-changed throughout, her sequences as President of the Time Lords largely boiling down to uninspiring political jargon and the odd ‘rousing’ speech to her High Council cohorts in the midst of their race’s entrance into an alternate dimension. Before any viewer who has recently been thrilled by The Day of the Doctor anticipates an insight into the ongoing conflict of the Keepers of Time whilst trapped in a pocket dimension, they should be reminded that James Peaty, Una McCormack and David Llewellyn wrote their respective episodes of this spin-off long before the 50th Anniversary Special’s broadcast, and as such- barring a few refreshing references to a certain impending war with the Daleks - there’s nothing new to be gained here in that regard.

To her credit, Jameson fares considerably better in her return to the role of everyone’s favourite savage, in no small part thanks to Leela’s contribution to proceedings closely resembling that of The Invasion of Time, whereby the character finds herself separated from the planet’s core society and so subsequently must find her own way to further benefit Gallifrey in some shape or form. Enter The Sarah Jane Adventures’ Anji Mohindra, a perfect fit for the mysterious Outsider Maris, whose importance in terms of evolving Leela’s character arc becomes evident as the season’s opening instalment Emancipation and particularly its successor Evolution progress the overarching narrative towards its compelling final act. That a one-off bout on Casualty and appearances in BBC Three’s Some Girls have marked Anji’s only notable TV performances since Elisabeth Sladen’s passing is utterly criminal, yet the actress who gave us Rani Chandra displays promise in multitudes as Maris, making her a potent candidate for future roles in the Big Finish range if nothing else.

Had more performances from the diverse array of guest stars matched Anji’s incredible standard, then perhaps Season Five would have been presented with a greater chance of overall success, but as it is, Sean Carlsen (Narvin), Peter Sheward (Slyne) and Scott Arthur (Lukas) each either lack charisma in their portrayals or are restrained by lacklustre dialogue from the series’ latest scribes, and their Outsider counterparts don’t handle the material with much aplomb either. The other solitary exception, then, is Simon Fisher-Becker. Best known by Doctor Who fans for his recurring role as Dorium in the Steven Moffat years, Simon’s Science Minister Kavil is a breath of fresh, comic air into an oft-soulless run, ever the charmer and cavorter of the party and a superb example of British talent to boot. In much the same vein as Anji, should Simon ever feel the inclination to take up the offer of a further role in Big Finish’s Doctor Who ranges or elsewhere, we regular listeners shan’t discourage him from doing so.

Any reader approaching this review with even a mild interest in pursuing the Gallifrey range has no doubt already learned of the nature of the season’s cliffhanger, but for those still unaware of the narrative’s final development, suffice to say that it is an immensely tense and thus satisfying teaser for the series’ final run. Indeed, if each of the three episodes on offer here presented listeners with a similarly engaging climactic sequence, the box-set as a whole would warrant far greater recommendation than it does in reality. As it is, its narrative is varied such that despite its merits, the final scene itself acts as a jarring tonal juxtaposition to everything that’s come before, therefore highlighting rather than concealing the inherently tedious nature of proceedings this time around. What might- in another dimension- have once acted as a simultaneously captivating and tonally cohesive denouement, then, instead acts only as the instigator of the disconcerting rhetorical dilemma as to quite why the ensuing level of tension and anticipation for future storylines only emerges in Season Five’s closing stages, rather than remaining a constant factor worthy of praise from start to finish.

Quite honestly, that final dilemma was the most prevalent resulting impact of Gallifrey V on this reviewer. Given that the notion of exploring the Doctor’s home planet before its destruction (and indeed its resurrection not too long ago) remains such an exhilarating prospect, and one arguably never truly fulfilled on-screen save for The Deadly Assassin, the writing team’s caution towards stepping beyond the frontiers of political drama here is confusing to say the least, particularly in light of the lukewarm reception to The Trial of a Time Lord’s similar approach. Hope may at least reside- in Louise, Anji and Simon’s performances, as well as Arbitration’s climax- that Big Finish can turn the tide in order to ensure that the Gallifrey range ends on a high, but a misstep so noteworthy at this late stage in the game bodes ill indeed. The Doctor’s “new destination” may well be his revived home planet, yet if the quality of his show’s latest spin-off continues to decline at this rate, then he needn’t bother commencing his search anytime soon.