Nick Frost, 38
As an actor, Frost is best known for his roles in the award-winning TV series 'Spaced', the critically acclaimed films 'Shaun of the Dead' and 'Hot Fuzz' and last year's Martin Amis adaptation 'Money'. He lives in south London with his partner
I've never been in awe of film stars – it's just their job – so when I first met Bill, on the set of Shaun of the Dead [Frost's first film role] in 2004, I just chatted to him like a mate, which set the tone, I think.
It was while we were filming The Boat that Rocked two years ago that we reached a tipping point in our friendship. Bill's character runs this pirate-radio station in the 1960s. One day I went up to [the director] Richard Curtis and quietly said, "Richard, I don't want anyone to know, but I've never heard anything from the Rolling Stones." So he bellows out to Bill, who is a Stones fanatic, "Bill, come here!" and they went to town on me with the teasing. Bill made me buy loads of their albums, and we connected over that.
Now we operate a musical exchange. Bill will say, "Listen to this track by [the 1960s rock band] the Yardbirds," and I'll play him some pumping hard-house track by Andy Whitby. When I paint a picture to him of dancing for 12 hours in an orgy of house music and poppers, I think he understands the feeling – it would have been like him going to a Hendrix gig.
These past 12 years my career has been like an apprenticeship, and Bill has been the perfect person for me to watch: he's a gentleman on set, making it his job to know everyone, from accountants to the grips; and the way he delivers his lines, he makes it look effortless. So I quietly keep my eye on him and there is an element of student-teacher dynamic, but I'd never let him know that. Instead I'll come up to him after a take and say, "I see what you did there, but why don't you just knock about 90 per cent off?" He never overacts, though; I just like teasing him.
We discovered a mutual love of food, so we set up a bi-monthly lunch club. We've been to Noma, in Copenhagen, which was beautiful, and most recently we visited Bar Boulud at the Mandarin Oriental in Knightsbridge. They brought out these platters including pig's head cheese, and I thought, "I'm not eating that." But Bill's adventurous, and dived straight in, so I had to try it too, and I have to admit, it tasted amazing.
Bill Nighy, 61
A prolific stage and screen actor, Nighy's portrayal of ageing rocker Billy Mack in the 2003 film 'Love Actually' catapulted him to international stardom, his subsequent films taking in hits from the 'Pirates of the Caribbean' franchise to 'Harry Potter and the Deathly Hallows'. He lives in London
In Shaun of the Dead, my largest part was to bleed to death in the back of a Jaguar. It involved a foot pump with a tube going up my trouser leg and shirt, pumping sticky fake blood all over my neck and down my clothes, for three days straight, during one of the hottest summers in memory. And Nick just made me laugh. There were six of us in the car, and it could have been terrible, but he made it pleasurable.
After Shaun, he continued to call and text and it became plain we'd developed something beyond the gig, which was unexpected, as I'm always surprised if a friendship emerges with another actor. It wasn't until The Boat that Rocked that I discovered what a musical weirdo he is. He claimed never to have heard a Stones record, which I thought was said just to taunt me, as I'm a huge fan, but it turned out to be true. He likes that deep Euro death-trance-dance-house; wordless machine music. I'm not a closed mind, though, and he's promised to make me a mix tape as a primer to his world.
As a rule, I dislike travelling with other people, but Nick is an adorable companion. On a trip to promote The Boat that Rocked, he developed a constant comedy limp in public, just for me, to cheer me up. He'd walk across a hotel lobby with a hobble, the like of which you've never seen before, with people looking on in shock. He limped all over Australia, Germany and Holland.
With acting, it's not a question of age or experience; people like Nick come ready-made, so he needs no instruction from me. If anything, I try to pick up tips from him on how to be amusing. While he has a fear of being "found out", it's something I've always worried about too, of being tapped on the shoulder with someone saying, "What the hell are you doing?"
We made a trip for Comic Relief last year to a 2,500-acre toxic rubbish dump in Kenya, where kids have to compete with wild pigs to find rotting food; it's hell. I've done a couple of trips with Oxfam, but this was the worst I'd ever seen. It was Nick's first, though, and as a very compassionate bloke, it took his breath away. When you share something like that – so outside your usual experience – it makes you closer and it's enriched our association.
'Paul' (15), a sci-fi comedy starring Frost, is in cinemas from tomorrow