This classic Doctor Who box set includes the fourth Doctor serial and K9’s debut, The Invisible Enemy, and A Girl’s Best Friend, the pilot episode of abandoned spin-off series, K9 and Company, which is still being talked about amongst Doctor Who fans despite having aired over 25 years ago.

Set in the ever-popular 51st Century, The Invisible Enemy sees Tom Baker’s Doctor and companion Leela answering a distress call from a shuttle crew on their way to the planet Titan. Arriving onboard, the Doctor finds the shuttle’s inhabitants either dead, or under the influence of a virus which both exerts psychic control over them, and proffers a set of fabulous glittery eyelashes that Girls Aloud would be proud of. Whilst certainly not the most memorable of serials, The Invisible Enemy is not without its charms; despite never quite picking an accent and sticking with it, Frederick Jaeger shines as K9 inventor, Professor Marius. Tom Baker’s Doctor is as funny as ever, particularly in the third part, where – brilliantly – he and Leela are shrunk down to minus-size and, erm, injected into his own brain.

Despite being his debut episode, K9’s appearance is fleeting; he doesn’t even turn up until part two, and is pretty much reduced to a wobbly-wheeled talking cannon throughout. There’s none of the – ahem – sparkling wit of his later appearances, as he becomes the Doctor’s companion, although it’s a decent enough introduction. Even though being almost universally derided amongst fans, K9 and Company fairs slightly better in terms of the finished product. Whilst not exactly ground-breaking, this well-worn supernatural story of regional-accented hill folk versus book-reading boffins – like a teatime edit of The Wicker Man, complete with pagan rituals, goat masks and pentagrams – is an interesting direction for a Doctor Who spin-off; indeed, K9 is the only thing approaching science fictional, and the titular company and a few brief mentions of the Doctor the only thing linking this to the Whoniverse at large.

Again, however, the episode is less about K9 and more about the company he keeps. Namely, Sarah Jane Smith, played – brilliantly – by Elisabeth Sladen. Sladen’s Smith – decidedly frostier now than when she travelled with the Doctor (as you would be, if you’d seen all the wonders time and space had to offer, only to be dropped off in Aberdeen, of all places) – carries the episode as it becomes increasingly ridiculous, somewhat laden down by her companion, Brendon. Shoe-horning in someone for the younger viewers to get attached to in the form of Sarah Jane’s cousin – a boarding school boy with a penchant for botany and getting captured by crazy pagans at the drop of a hat – was never going to be a wise move, particularly when the character in question is a slimy smart-arse with a haircut at least two decades out of fashion.

But, whilst far from the best television has to offer, it’s a reassuringly good-natured production, with everything back in its good and proper place in time for a resolution of tea and crumpets and K9 singing ‘We Wish You A Merry Christmas’. Yes, really.

Both DVDs come with the usual wealth of extras, including commentary tracks – sadly lacking Tom Baker – and the obligatory handful of celebratory documentaries; mostly, Terrance Dicks, John Leeson and whoever was making tea in the office when the respective episodes were written waxing lyrical on the tin dog’s virtues, explaining – perhaps even justifying – his perceived popularity.

Though certainly popular with the younger set – and the vocal minority of fans still championing animated spin-off, The K9 Adventures – it’s hard to see just how the tin dog merits his own boxset. Whilst occasionally witty, if you like that sort of thing, he is – essentially – an exposition machine, serving as a shortcut for writers in much the same fashion as the Doctor has been using his souped-up sonic screwdriver in the revamped series. The extras will certainly satisfy the die-hard fans, but for the rest of us K9 might just as well be reserved to fond memories and the occasional cameo.