‘Finally, face to face. It’s the clash of the nerds.’ Luke returns to Bannerman Road in time to meet his new “sister” and join his mum investigating the mysterious Joseph Serf, a Steve Jobs type responsible for the new wonder-computer the ‘SerfBoard’. In her final story, Sarah Jane’s journalist credentials are reforged – she’s one of the country’s best, and, as she reminds Clyde and Rani, it’s this that pays for her lavish lifestyle. We even get to meet her first editor, the lascivious Lionel Carson (Peter Bowles, bringing more “gentleman of a certain age” stylishness to the show in the wake of Nigel Havers).

We haven’t seen Sarah Jane at work quite like this since she went up against Hilda Winters at Think Tank: her scenes with Serf (a superbly smooth Mark Aiken) drip with thinly-veiled barbs and insinuations while Aiken’s “assistant” (a camply condescending James Dreyfus) tries to give as good as his master gets.

Meanwhile, ‘Clani’ are left behind in the attic picking over a SerfBoard with the help of Mr Smith at his unflappable best. This allows some space to explore the new ‘Skuke’ dynamic as Luke teams up with Sky, the little sister he didn’t particularly want, to investigate behind the scenes of Serf’s business. They discover a tribe of Jawa-like creatures controlling Serf like he’s some sort of Teselecta, led by an unmistakeable Dan Starkey in a rubbery Cyclops prosthetics. This is funny, characterful, fast paced and borderline farcical – in short, a typical Gareth Roberts script.

Next Time: The Man Who Never Was – Part Two