Mad Men cast unveil season 4

Three years after it first hit screens Mad Men is still one of the most popular and critically acclaimed shows on TV. The US series has four Golden Globes to its credit and achieved 17 nominations at the 2009 Emmys. The key to its success, according to its star Jon Hamm, is the hard work put in by those who work on it.

"It's why our show feels so accurate, we have, from Jane Bryant, who is our costume designer, to Dan Bishop, who is our art designer, to our construction crew and everything, everyone takes their job very seriously and tries hard. And that shows in what I think is the quality of our show," said Hamm.

The US actor plays heartthrob Don Draper in the 1960s drama, set around an advertising agency.

"We are this kind of scrappy upstart in many ways, we shoot during the summer when the whole lot's empty and we don't really have the big fancy lot or the big trailers or any of that kind of stuff. But we still try to put out the best show we can," added Hamm.

Hamm and co-stars including Elizabeth Moss and Christina Hendricks walked the red carpet in LA to launch Mad Men season 4, but were keeping tight lipped about the new instalments:

"I mean you'll have to see it and find out," said Moss.