WAS he mad, in a coma or back in time? Millions of viewers saw the stunning finale to Life On Mars last night at the end of a two-year TV rollercoaster ride.

Speaking for the first time about both the conclusion to the BBC1 drama and the new spin-off series, co-creator Matthew Graham revealed it was all about Sam In Wonderland.

First, the good news. It was already known that Philip Glenister would return to the role of DCI Gene Hunt in Ashes To Ashes, set in 1981 London.

Now it can be confirmed that filming begins this summer, when the Gene Genie will be joined by DS Ray Carling (Dean Andrews) and DC Chris Skelton (Marshall Lancaster), with all three transferred from North West District CID to the Metropolitan Police. It's due on screen next year.

Aside from Eighties' fashions, Gene will also have to cope with a sexy new female sidekick, DCI Alex Drake, who has yet to be cast. After an accident in 2008, the no-nonsense detective finds herself back in time, interacting with characters she'd previously read about in reports logged by a certain Sam Tyler.

"We like to say it's Moonlighting meets Miami Vice with a smattering of Howard's Way," laughed Matthew. Gene will also swap his Ford Cortina for the original Audi Quattro. "We've already coined Gene's new catchphrase, which is, `Ray, fire up the Quattro!'

So, why the switch to London? "We felt like we had to really change things, make it look different and feel different. And it's really hard in Manchester. We've used a lot of the locations."

But how do you follow a drama as brilliant and loved as the two series of Life On Mars? "I was unsure about the whole idea. I thought we were milking the cash cow - until I started writing.

"We had story conferences where brilliant ideas were thrown around and we got very excited. But still lurking at the back of my mind was that feeling, `Is this right? Shouldn't we just be leaving it now?' And then I started writing it and the world sprung into my head. It felt so clear what we were trying to do.

"It's going to feel like Life On Mars but bigger and with a real sexual chemistry between the two leads."

Which brings us to that ending, which saw Sam (John Simm) waking up from his "sunken dream" coma back in the modern day, where he struggled to feel alive.

It was the ending that Matthew and his co-creators had planned from the very start.

"It was much more important that there was a strong emotional closure to the story. That was more important than a massive twist.

"I was always slightly surprised that people thought there was a genuine mystery. To me, it was obvious - he got hit by a car, the doctors and nurses were speaking to him over the radio and through the television and he was in a coma. The fact is that he began to suspect there seemed to be a way in which he could change his world - once he's there for a period of time, he begins to assimilate so much of that world into himself. He starts to question whether he was ever anywhere else.

"But I never thought the audience would fall for that. But then we realised we had to start being a little bit more careful about saying definitively that he was in a coma.
Matthew added: "It's not supposed to be a searing indictment on modern society, but more a comment on Sam.

"He was a deeply repressed human being - I don't think 2006 or 2007 brought out the best in Sam. When he went to sleep, he wanted to be in a freer place, a place where his mother was a young, beautiful woman and his dad was his hero, and it was a world of fast cars - that was his liberation."

Life On Mars was more than just a hit drama. It made a real emotional connection with its audience.

"People love to watch those characters. They feel a great affection for them and, ultimately, it's not a cop show and it's not a time travel show, it's Alice In Wonderland, that's what it is.

"And that template of a journeyman, going through the looking glass into a magical world is an archetypal story. It's the fantasy journey."

John Simm made clear last year that he would not be appearing in the spin-off and there are no plans to involve him. So is this the last we'll see of Sam Tyler, happy in 1973 cop heaven? Matthew's not sure. "You shouldn't write him off completely. You never know with Life On Mars."