Jon Hamm - It's all started to ad up...

When Jon Hamm walks into a room, there is an aura about him that makes it easy to see why all the secretaries in the office swoon as he steps into his office as Don Draper in Mad Men. He dresses smartly, with a blazer over a shirt, has a more muscular than expected frame and gives off an air of confidence that comes from being one of the most sought-after actors on the planet.

Playing the mysterious marketing man in the 1960s-set TV series has made the St Louis-born star a household name across the globe. He's been translating some of that charm onto the big screen recently, with his appearance in the Allen Ginsberg biopic Howl coming hot on the heels of his turn in Ben Affleck's The Town.

In Howl, Hamm plays Jake Ehrlich, the real-life attorney charged with defending Ginsberg's seminal poem at the groundbreaking obscenity trial that took place in San Francisco in 1957. The trial established the framework for freedom of expression and how the US First Amendment related to artistic work. The charismatic Ehrlich wrote a book about the trial called Howl of the Censor and his life inspired the TV series Perry Mason.

In The Town, Hamm was also on the side of the good guys, playing an FBI agent pursuing a team of criminals. Both of these roles are far more honest and clean-cut than his 60s advertising exec. In the forthcoming Sucker Punch, however, an action-fantasy described by director Zack Snyder as "Alice in Wonderland with machine guns", the actor plays a character known as High Roller, a client at an imaginary brothel who is hell bent on taking the virginity of a young girl called Baby Doll.

The actor, who turns 40 in March, says, "I guess the difficulty with playing in a television series is that you get to play the same role over and over again. And while it's fun and I love dong the show, it is nice to get the opportunity to do different things. What I've tried to do for the majority of my career is to do things that are challenging and exciting in different ways."

Hamm, like George Clooney before him, struggled for recognition until the right part in a TV series established him as a heartthrob. He claims that as a young actor he always looked ten years older than he was and so could not get parts that his peers were winning. One of his oldest friends is the actor Paul Rudd, who he would visit in Hollywood in the early 90s before making the move to Los Angeles. He worked as a waiter and was dropped by his agency before his luck began to change when, in 2000, he won a part as a fire fighter in the NBC TV drama Providence.

One of the things that kept him going through this period was a sense of humour that veers into the characters he plays on screen. "I wouldn't call myself a funny guy," he opines. "I try to be light-hearted. Sometimes the work we do can be serious and so I try to – you English have a wonderful expression – take the piss out of people."

The actor has been dating actress Jennifer Westfeldt since 1997. In 2001 he appeared in Kissing Jessica Stein, in which his partner starred. The couple started the production company Points West Pictures in 2009. "Me and my girlfriend are producing a feature film which we're shooting in New York," he says. "It's the third film that she's written and starred in after Kissing Jessica Stein and Ira and Abby, and this one is called Friends with Kids. We're both in it."

The film, also starring Megan Fox and Adam Scott, is about two friends who witness all of their friends having children and decide to have a child together while still dating other people.

The ability to work together and take their career into their own hands is a boon for the pair, whose heavy workloads can easily keep them apart for months at a time. They work hard, he says, to ensure a work/life balance. "She's working on things, and I'm working on things, but you want to carve out time for living your life as well – and we've been very diligent about that and we've been lucky. After all, it's a good problem to have to have so much opportunity in our careers."

On wearing the producer's hat, he posits, "Well it's all new to me. The worst part is that you hear 'no' a lot and you have to ask people for favours. The best part is that you get to create something from the very early stages."

After his early career spent not having an opportunity to work, Hamm is finding life on the other end of the spectrum equally tough. "You have to make time; I could probably, if I wanted to, work 365 days of the year, but you do get exhausted. I did eight months straight with Mad Men, The Town and Sucker Punch. Life is too short; you definitely want to live life as well."

Home comforts are definitely something that Hamm values in real life as much as his character Don Draper does on Mad Men. "We have very good friends in California, and we have good restaurants and wine and its nice to unwind that way. And that's what is good about having family: you know you can come home and the dog is there, there's a fire in the fireplace and you can just let it all go."

Preparations are also under way to commence filming on Mad Men series 5. Hamm doesn't think that this series will necessarily be the last: "I think we'll keep going as long as the story is interesting to tell – and I don't know how long that will be. We've now shot four seasons, 52 episodes of it, and I think there are a lot of deep dramatic stories still to be mined in that character. I'm glad I don't have to think them up; I'm glad it's someone else's job. But I'll keep doing it as long as they will have me."

Showing his funny side off, he appeared in a handful of episodes of the Tina Fey-created show 30 Rock early last year, playing a hapless doctor. Despite the movie gigs, doing more TV is something that Hamm wouldn't rule out when Mad Men does finally run out of legs. "Depends on the show. Honestly, I think there is some tremendous work being put on air right now. So sure, if it was a good show, with a good role and I got to work with good people; I would never say never to anything."

'Howl' is out on 25 February; 'The Town' is out on DVD on 31 January; 'Sucker Punch' is out on 1 April