''All good things come to an end,'' Hamm says, simply.

''I don't want to be on a show that overstays its welcome and I'm not interested in being on a show that just runs forever either.

''We watched Breaking Bad and 30 Rock, we've watched these shows that for one reason or another have had endings put on them. And I think they've all been successful in their third act, in their final act, and I hope that ours is as well.''

The final season of Mad Men will be played out in two parts. The show's producer, Matthew Weiner, has not articulated a vision for the conclusion of the series publicly, but there is no doubt he has one very carefully framed.

For his part, Hamm says he's in the dark but understands why the conversation about the end of a show has become so important.

''The era of television we're in right now, it's an incredibly lucky time if you like television, which I happen to,'' he says. ''When you see shows like our show or most recently True Detective, these stories that have a beginning, middle and, most importantly an end, you expect as a viewer that they come to a satisfying conclusion.

''As for how much input that I have on [Mad Men] that is negligible,'' he says. ''I don't have any creative input on the show other than what I bring to it as an actor. Matt's been very clear I think in all of the press and all of the surrounding intelligence about the show that, you know, it's very clearly his baby and we are simply servants to that vision and that's fine and that's as it should be.

''I don't have any input really in that world. And I honestly am kind of happy that I don't because I don't want to have to think up the end of this thing. It's been, you know, seven seasons of characters advancing and honestly I'm glad I don't have to think it up. I'm glad I just have to memorise lines.''

So, Mad Men may one day be consigned to the back shelf of television masterpieces. Not too grim a fate, given it will keep good company in The Sopranos, Breaking Bad, Damages, Dexter and the slew of other not-long-gone greats.

But Hamm's alter ego, the dashing, deeply flawed Don Draper, may take a little longer to forget.

''Well, he's not a very lovable guy so there's that but I would suggest that he's also not very hateful either so I think that the emotions I feel toward that character are somewhere in the middle,'' Hamm says. ''But a very wise man told me once about acting that if you ever judge the character that you're playing, you're going to do it a disservice and so I try not to judge our guy, Don.

''I just try to humanise him as much as I can and I think that that's maybe been the biggest challenge of portraying this guy who is fairly odious in his behaviour patterns.''

The show's final season will take two years to play out, in two blocks of seven episodes. The preceding season finished with Draper revealing that his life, or at least his life as the audience perceived it, was a carefully constructed lie.

Coupled with a turbulent personal and professional life, it has become, Hamm agrees, a fascinating study on the deconstruction of a man.

''It's generally an interesting narrative arc, what you deal with, with the decline [of a man]. It's a well-worn trope in storytelling, from the Greeks, so I think it works,'' he says. ''But I wouldn't load any more gender politics into it than need be. It just is what it is.

''It's also concurrent with the rise of other people in the story as well. You can point to some of them like Peggy Olson or Joan Harris or even Betty. So, as one person's boat is foundering, someone else's is experiencing, you know, full sail. I think that that's a perfectly legitimate storytelling device.

''We started the show with Don Draper at the top of his game and at the top of his world and he's certainly not in that place any more and I think that that's a pretty good narrative place to begin the final season.''

In the show's sixth season finale, we saw Don unravelling dramatically. Hamm isn't saying much, but he does believe that Don has a track record of stepping up when the heat is on.

''It was a big deal for Don to be essentially fired and I think that… it's a bit of a wake-up call. Will it have the desired effect? Will it have the intended effect? I don't know. I mean, I do know because I've shot the first half of the season but I'm not going to tell you.'' he says, laughing.

''But I think that the one pattern we've established with Mr Draper is that he tends to rise to challenges and I think that that's a fairly real, established pattern in Don's life. When he is challenged or at least pushed far enough, he will push back or rise to the challenge. I think that's basically a bit of a hint as to what we can expect in the final episodes.''

The series has, in its six-year life, brilliantly used its 1960s-era setting as a platform to tell provocative stories about infidelity, sexism and homophobia.

Hamm believes the power of that story-telling lies in the familiar.

''The 1960s is far enough away from our current time to seem different and yet close enough to our time to seem familiar, if that makes any sense,'' he says.

''So, it seems like it was very far away and that was, oh, look at everybody smoking and wearing funny clothes and different hats and talking to each other differently, and yet, the behaviour patterns are familiar to us.

''It's not that old-timey, we're not Downton Abbey. And yet there's this other quality to it so we recognise that it's different and it's in the past and yet it seems so familiar to us still that we wonder how much in fact have we really changed from what is now solidly a few years ago.''

Mad Men, Monday, Showcase, 4.30pm and 8.30pm.