In 1973 I was six. I liked Doctor Who, Star Trek, The Goodies, playing with Airfix toy soldiers, LEGO, and reading. I had younger twin sisters, and I usually got into trouble being rotten to them. It was also the first year that I received a present from my parents that to this day I do not understand why I was given it. Otherwise, life was good.

In 1973 Sam Tyler is four. He likes playing with toy cars, going to see Manchester United play with his father, and wants to be a policeman when he grows up. Apart from his father being away a lot, life for Sam Tyler is good. Except that Sam Tyler (John Simm) is also 35, a detective inspector in Manchester & Salford CID, working a system he believes to be the policing equivalent of the Dark Ages, and for a boss he just about respects but thinks a thug. Sam Tyler is also seriously out of his depth. Because in reality, Sam Tyler is a detective chief inspector in the Manchester Constabulary in 2006. For Sam Tyler, life is not good.

This is the setup for Life on Mars, the hit BBC television series from 2006. It is a time travel drama that explores the clash between the 21st century police procedural and the hard hitting cops ‘n' robbers shows of the seventies. In fact, an apt description of the series might be Quantum Leap meets The Sweeney, but with the most disturbing version of Rear Admiral Albert "Al" Calavicci you will ever see on television -- The Sweeney being the archetypal cop show of the period wherein the average copper is hard living, hard drinking, hard womanising, and likely to use his fists and yell, "Yerr nicked!" when carrying out an arrest.

Gene Hunt: [To Sam] Where are you today, then? Here, or Planet of the Clangers?

Life on Mars begins with DCI Tyler knocked down in 2006, the victim of a hit and run. He awakes to find the last song playing on his iPod -- David Bowie's Life on Mars -- playing on his car's eight-track, and his suit replaced with a wide-collared shirt and a leather jacket. Now a D.I., Sam is no longer the boss, but the number two in the Serious Crime Squad under D.C.I. Gene Hunt (Philip Glenister). Wearing white slip-on loafers and a camel-hair coat, Hunt embodies the prejudiced, chauvinist attitudes of 1973, as do most of his squad. Fortunately for Sam, he has a confidant in Woman Police Constable Annie Cartwright (Liz White), but as attracted as she clearly is to Sam, even she grows exasperated at his tales of the future.

[After Sam, disorientated and confused by his new surroundings, has challenged Gene's authority]

Gene Hunt: They reckon you've got concussion -- but personally, I couldn't give a tart's furry cup if half your brains are falling out. Don't ever waltz into my kingdom playing king of the jungle.

Sam Tyler: Who the hell are you?

Gene Hunt: I'm Gene Hunt. Your D.C.I. And it's 1973. Nearly dinner time. I'm 'aving hoops.

A new take on the classic fish out of water tale, Life on Mars lets us look back on -- if not a fondly remembered era, at least a look back upon that era through a fondly remembered television format. With the addition of some humour, it examines the culture clash between Gene Hunt's 1973 world of chauvinism, prejudice, and even racism, and the political correctness of Sam's and our 21st century. Issues explored include the small-scale corruption institutional to the police of 1973, the decline of both industry and the unions, football hooliganism, and for Sam, childhood memories.

Even as Sam gets to grips with 1973, there is the question of how he got there. Is he a time traveller from 2006, or is he in a coma in 2006 and this is all going on in his head? The series never makes this clear, but throughout Sam hears voices from his hospital bed in 2006 and is frequently addressed by characters on his television. Usually by an Open University lecturers, or in the series' truly creepiest moments, by the little girl from the BBC Test Card, who actually steps out of the television. Small girls with clown dolls are just not right.

Test Card Girl: Do you not like me with my clown? I can see I make you frown. When on Earth will all this end? I'm your friend, your only friend.

Although some might nitpick the details -- that the cars are not quite right or that the police terms are inaccurate -- the look, the feel, and the sound, which employs some of period's best glam rock tracks, are perfect. Together they capture the feel of the series' inspiration, The Sweeney. This shows in the car chases, often in the series' signature car, the Ford Cortina (the original title for the series), though foot chases can sometimes be as good, and even as funny. And also in the whipcrack-sharp dialogue -- much of it delivered by Gene Hunt, and by modern standards, invariably highly inappropriate.

Gene Hunt: I think you've forgotten who you're talking to.

Sam Tyler: An overweight, over-the-hill, nicotine-stained, borderline-alcoholic homophobe with a superiority complex and an unhealthy obsession with male bonding?

Gene Hunt: You make that sound like a bad thing.

The first series is available on DVD, and comes with a "Making Of" documentary or two, and audio commentaries on all eight episodes. The BBC is showing the second and unfortunately last series, in which the writers have promised to wrap and explain the mystery central to Life on Mars. This series is also stronger in tone, having already dealt with police racism, major police corruption, and the sexual politics of 1973. The second series will be released on DVD shortly after it comes to an end. There is also talk of a sequel set a decade further on, but without John Simm and the character of Sam Tyler. Which is all the more disappointing because the interplay between the two leads of Glenister and Simm have been a delight.

Sam Tyler: We pull him in, we put the squeeze on him. Why is that so hard for you to agree to?

Gene Hunt: Because I am policing in the full glare of the public bloody eye, and the Chief Super is taking a personal interest and we also have no flipping evidence! And I can't believe I just said that!

Life on Mars is one of those series that keeps its genre elements quiet enough that it can successfully be broadcast on mainstream television. Had those genre elements been stronger or more obvious, and the series might not have found a place at all outside of the genre niche.

That genre is more fantasy than science fiction, and for the most part it hides this under the culture clash between the police procedural and the machismo of the seventies cop show. Ultimately, it is this clash that gives Life on Mars much of its entertainment value and makes the series just so much fun.