"I think the casting lady mentioned it and Jane says to me 'oh I loved that film have you seen it?'. To me. I said 'I f***ing directed it ... you've just made up for my f*** up.'
"That was it. Instant bonding. I got the gig the next day."
Another embarrassment is one TimeOut brings up - Mullan vowed with three other British actors in 2009 never to work for the BBC again after the British broadcaster refused to screen a charity appeal for humanitarian aid in Gaza. But here he is in the BBC-backed series, albeit one which also has some American money behind it, Australia's ABC having pulled out due to casting decisions.
"I know I can't believe this is BBC money. I am embarrassed. I made a declaration I would never work for the BBC again," he says, adding that of the four, who included Samantha Morton, he was the longest to stand his ground and that he didn't realise who was behind the production.
"Within six months a meeting was called and three of them said 'we are all skint and the BBC has offered us work'. "I was the only one who wasn't going to work for the BBC again. That's really going to sink the longest working public broadcasting unit in the world."
"I'm f***ed on that one, totally," he laughs, saying he expects he'll be called on it again by the British press when Top of the Lake screens there.
Oh, and he has one minor embarrassment when it comes to being in New Zealand. He auditioned for The Hobbit. James Nesbitt got the part. He hates it when auditions don't go his way.
But the gregarious, hilarious Mullan would seem to have nothing to be embarrassed about when it comes to his performance in TotL - the first episode shows that, Scots accent and all, his Mitcham is as charismatic as he is menacing. "He's a tortured soul ... there's a lot of self-loathing there but on the whole, like any lunatic I've ever met, he doesn't see himself as such. He has more than a few dark nights of the soul, and the power that he wields over people - it's a hands-on power. It's not the gangster from afar whose reputation can do things. He's hands-on.
"He's sort of guy who thinks 'I haven't beaten up anyone this week so I am an okay guy'.
Mullan admits to some confusion about why, in the New Zealand setting, his character speaks with a broad Scots accent and his mother is buried here.
"I wouldn't blame anyone for saying why is the Jock there?"
But that's just the way it is in Campion-land and he likes it.
"It doesn't seem to bother Jane in the slightest. Which is another thing I love about her. It's not a weird or kooky thing because she doesn't give a f*** about a lot of things. It's something I really like. She's really brave. She's, 'I just like it, enough!'. You don't get the usual panic about what others might think. Jane genuinely doesn't care."
He's thankful too that, as a key player in the cast, his performance isn't likely to be cut like previous ones ...
"I was the star of Trainspotting and they just changed the whole thing. I know that sounds hard to believe but that was my movie and that [expletive] McGregor comes along he does his Lust for Life whore acting and they cut me out of the f***ing thing.
"Braveheart was mine too. I came out as a spear carrier. That was my movie."
Er, how about his last big movie, War Horse?
"War Horse was mine too. I had a whole love affair with the horse and they cut it out, the bastards."
What: Top of the Lake
When and where: Monday 8.30pm, UKTV
Listen to the full round-table interview with Peter Mullan and David Wenham below.
- TimeOut
