"Your ex-wife is here": Betty Francis (January Jones) and daughter Sally Draper (Kiernan Shipka) scan the party scenery as Don's new wife Megan (Jessica Paré) breaks the news to her suave husband(Hamm)

The new season will air in the US in April with a two-hour opening special. The cast has jumped in time to 1967, with the show's creator Matthew Weiner explaining to US TV Guide: "I love writing that first episode as if the audience knows everything that has happened, and watching them piece it in their head. It's an elliptical experience."

'Mad Men' is back