The series has been one of the BBC's biggest hits of the year

Around 6.6 million watched the first half hour, with the audience growing to 7.7 million once Manchester United's Champions League clash ended on ITV1.

Fans of the drama finally found out how modern-day policeman Sam Tyler, played by John Simm, ended up in the 1970s.

A sequel has already been announced, with the action moving to the 1980s.

The average audience for Tuesday's show was seven million - the highest figure for the entire second series.

"We're delighted so many people tuned in to see how Sam Tyler turned out," said a BBC spokeswoman.

The show's climax was open to interpretation - and internet message boards are still full of speculation about whether Sam Tyler was mad, in a coma or back in time.

Award-winning

Actor Philip Glenister (left) will have a female co-star in the sequel

The first series of Life On Mars won an international Emmy, and it has been reported that a US version of the show is being made.

Series two has just received three nominations for the Bafta television awards, including best drama.

One of the show's biggest draws has been politically incorrect DCI Gene Hunt, played by Philip Glenister.

He will return in the sequel, called Ashes to Ashes, which is to be set in London in 1981.

But Simm's character will be replaced by a female detective from the 21st Century who is stuck in the past after an accident.

Filming is due to begin this summer and the show will be broadcast on BBC One next year.

On ITV1, an average of 6.3m people tuned in to watch Manchester United's 7-1 Champions League quarter-final victory over Roma.

The audience peaked at 7.2m at several points during the game, which United manager Sir Alex Ferguson said was their greatest European match at Old Trafford.