The last adventure in the long and illustrious career of journalist, mum, erstwhile Doctor Who companion and proper bloody legend Sarah Jane Smith isn’t the best story which she’s ever been involved with, but it contains enough humour, pathos and excitement to ensure viewers of all ages will get something out of her final bow – and that’s what counts.

Sarah, Sky and Luke attend a preview of a new laptop called the Serfboard and immediately discover something is amiss with the device’s Philip-Schofield-as-Bill-Gates creator, Joseph Serf. More than amiss, really – he actually died a long time ago and now only exists as a hologram powered by monocular, Jawa-like aliens called Scullions who are enslaved by Serf’s assistant, the loathsomely evil Mr Harrison whose master-plan is that typically mundane, human goal: the accumulation of a vast wad of cash.

James Dreyfuss (Gimme Gimme Gimme) fairly revels in the role of this pantomime villain, the quasi-Bond-baddie one-liners fired out with a vehemence that PC Goody in The Thin Blue Line would never have been able to muster. ‘Tea? Coffee? Anthrax?’ he bitches during Sarah’s interview with Mr Serf before having her locked up with a dismissive snort of, ‘What are you going to do – hit me with your handbag?’

A lot of his snarkiest remarks will fly well over the head of the youngest viewers; as will some of Gareth Roberts’ nudge-nudge adult gags (‘Proper smile, not sexy smile!’ moans Plark as the Scullions lose control of the Serf hologram, while Sarah later purrs, ‘When it comes to men, I prefer something I can grab hold of’), which culminate with Mr Smith spelling out the potentially perilous phrase ‘GRAB HARRISON’S PEN…’, leaving Clyde goggle-eyed with Carry On amazement until he realises that’s the end of the final word. ‘I’ve never been so glad to see a full stop,’ he quips with relief. The kids may not know what the hell is going on, but we laughed so hard at this moment we had to rewind and watch it several times over.

You can have too much of a good thing, of course, and the comedy ultimately overpowers the dramatic heart of the story. Even the sledgehammer subtly of the parable about the slave trade (a continuation of the mature themes worked into the previous two stories), is buried beneath the slapstick of Mr Serf’s hologram constantly going wrong (making him dance like Ian Curtis at one point and sound like Arthur Bostrom in ‘Allo ‘Allo! at another) and a ceaseless stream of cracks about water torture, Mumsnet and Clyde and Rani having to play husband and wife – in practice for the future, no doubt.

Happily, all’s well that ends well. Nasty Mr Harrison is taken away by his former slaves in a spectacularly impressive spaceship (vastly better, in fact, than a very similar scene at the end of Matt Smith’s debut Doctor Who story), Luke and Sky stop moping at each other and realise they really are brother and sister after all and, best of all, Sarah Jane is shown at her very finest.

It’s hard to say what’s more affecting: her delight at the Scullions escape from enslavement or her poignant query at the end about the real, long-dead Mr Serf. Both are highlights that will live long and fond in the memory.

And then, it’s all over. Except it isn’t, of course, because after a montage of clips from all five series of The Sarah Jane Adventures (including shots of K-9, Maria and David Tennant’s Doctor) the final episode ends with the legend, ‘And the story goes on… forever.’

The series may be over, and Elisabeth Sladen may sadly no longer be with us, but Sarah Jane Smith will live on. As long as new generations of children are born, her adventures will always exist to delight and enchant. She’ll never be forgotten.

Aired at 5.15pm on Monday 17th October 2011 and Tuesday 18th October 2011 on CBBC.

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