Kaley Cuoco wanted 20 years of Big Bang Theory

Kaley Cuoco would have "done 20 more years" of 'The Big Bang Theory'.

CBS announced last month that the US sitcom would conclude for good after the 12th season and the 32-year-old actress - who has played Penny since the show began in 2007 - admitted she was left heartbroken when she head the programme was ending.

She said: "It's broken my heart. I am so sad that it's ending. For the record, I would have done 20 more years."

The news left the whole cast so stunned, they initially hoped it was a joke.

She told 'Extra': "I was bad, but everyone was crying... I think we were all hoping for a giant 'bazinga!' "

There have been rumours of a spin-off show, and though Kaley insisted she didn't know anything about the possibility, she'd jump at the chance to work with showrunner Chuck Lorre again.

She admitted: "If he called me and said 'let's do something' tomorrow, I would."

'The Big Bang Theory' is the longest-running multi-camera series in history and its final season is set to return to TV screens this week.

But co-creator Bill Prady recently admitted they hadn't made any big plans for the end of the saga.

He said: "We're approaching the final season the same way we've approached the 11 seasons before: with no planning whatsoever. From day one, we have never planned an arch for a season. We don't plan ahead, we just kind of just tell the next story."

But Bill already knows he's going to miss the cast - comprised of Jim Parsons, Johnny Galecki, Mayim Bialik, Melissa Raunch, Kunal Nayyar, Kaley , and Simon Helberg - because they all get on so well and have developed a strong friendship over the years.

He explained: "I'm really, really gonna miss these people. It's a cliché to say everyone is friends and we all get along, but everyone is friends and we all get along and we all love each other. I will miss them very much."