Ch-ch-ch-ch-changes. But are they always for the best? This, in the end, was the philosophical question posed by Life on Mars, the last episode of which (9pm, 10 April) was, amazingly, also the best of the series (I'd been expecting an effortful struggle to tie up several very loose ends). It turned out - and this will read like gibberish if you're not a fan - that Sam Tyler (John Simm) was in a coma, after all. But when he woke up, as we all suspected he one day would, the 2007 that he had been struggling to get back to for so long had lost its zappy, right-on, modern, Technicolor appeal. It was unexpectedly drab, bogged down in process, earnest, uncool. It also lacked a certain rather pretty female copper. And so, heart-stoppingly, Sam made a decision - how, I'm still not sure, though it involved jumping from the roof of an office block in Manchester - to return to 1973. Thus, the punctuating beep of his heart monitor was replaced for ever with the throaty roar of Gene Hunt's bronze Cortina.
I cannot remember the last time I enjoyed a television series so much as Life on Mars. Tyler, a cop, has an accident. When he wakes up, it's 1973. Is he in a coma? Or is he mad? At first, the time-travelling seemed to be merely a vehicle, albeit a very slick vehicle, for a bit of nostalgia - Remember the test card? Remember when the police drove Allegros? - and a lot of jokes about how awful the 1970s were. Tyler's boss, Gene Hunt (Philip Glenister), was straight out of The Sweeney: face like cheap ham, shoes like pasties. To him, Tyler, with his fondness for procedure and his touchy-feely ideas about "the community", was nothing less than a big fat fairy.
As a caper, it was always funny, but you did wonder if the effect would pall over time. It didn't; it just got darker, more sinewy. The final episode (although I'm in mourning, I'm glad the show stopped at two perfect series) brought into the open an implicit theme of Life on Mars: the idea that 21st-century life, while undeniably nicer, kinder and more equal than its 1973 equivalent, is also very lonely. What do iPods, mobile phones, computers and fast food all have in common? They isolate; they anaesthetise.
After Sam woke up in 2007, he attended a meeting at which his police colleagues discussed ethics. The giveaway here was that many of them were also hiding behind their laptops. Sam looked down, and saw that he had sawn across his thumb, a cut he couldn't actually feel. The 1970s, as conjured by Life on Mars, were gloomy and washed out, like an old Polaroid. Yet, in the final moments of the final part, the red brick of the back-to-backs burned like fire. Why? Had Tyler gone native? No. It wasn't the drinking, swearing, bigotry and testosterone he missed; it was how, in 1973, human beings - even the police! - used to talk to one another, face to face, in the flesh.
Can Life on Mars be faulted? Not by me. It worked as a drama, a fiendish crime solved every week; and it worked as a comedy, too, even if the jokes were aimed at those of a certain age (though seeing Gene disguised as Tufty, the road safety squirrel, is funny even if Tufty didn't teach you to look both ways). It was beautifully cast. Liz White as Annie, the only female police officer in the room, looked as if she'd strolled straight out of the pages of Jackie. Dean Andrews as the Neanderthal copper Ray Carling was a triumph of strutting aggression and ludicrous hair. The direction was razor-sharp. Most of all, though, it was beautifully written. Ashley Pharoah et al grew in confidence to the point where they could go off at bizarre tangents for no reason other than because they fancied it - Gene's solicitor singing "Let My People Go" in the interview room was just one delicious example. An actor as good as Glenister can breathe life into the wobbliest of lines, but, watching Life on Mars, you had the sense that he knew this was the gig of his career. He wore that camel coat with real commitment, and for that, I thank him from the bottom of my fickle TV-watching heart.
Pick of the week
Travels With My Camera
18 April, 10.30pm, More4
Inside crazy Turkmenistan with the critic Waldemar Januszczak.
Cutting Edge: Meet the Foxes
16 April, 9pm, Channel 4
A look at urban foxes. Love 'em or hate 'em?
Sea of Souls
17 April, 9pm, BBC1
Bill Paterson is a paranormal investigator. Spooky.