Both Robert Downey Jr and Val Kilmer have something of a reputation in Hollywood, so it should be no surprise that they hit it off when making a film together. Steve Pratt meets actors both labelled "difficult", although for very different reasons.

THE interview has barely started when Val Kilmer hears laughter coming from a neighbouring room. "What the ..." he shouts, leaping up from the table and storming into the adjoining hotel suite to confront the cause of the jollity.

He returns to report that Robert Downey Jr, his co-star in the action-comedy-drama Kiss Kiss Bang Bang, is holding court there with other film writers.

"Guileless snake. I hate him," snarls Kilmer, sitting down again to resume our talk. I'm not, however, witnessing first-hand a rampant Hollywood ego in action. Kilmer has gained a reputation for being difficult but on this occasion he's only joking, feigning annoyance at Downey's ability to make his audience laugh.

As for being difficult, the actor who played Ice Man in Top Gun and rock star Jim Morrison in Oliver Stone's The Doors is in jovial mood. He seems to have lightened up since the days when his on-set behaviour caused directors Joel Schumacher (who directed him in Batman Returns) and John Frankenheimer to state publicly that they'd never work with him again.

It's ironic that Downey is not only the object of his mock indignation but also his co-star as he too has a reputation in Hollywood, prompted by a drug habit that led to prison and rehab, and put his film career in jeopardy.

The pair obviously hit it off making Kiss Kiss Bang Bang, in which Downey plays petty thief Harry Lockhart who's thrown together with Kilmer's private eye Perry van Shrike - Gay Perry to his friends, for obvious reasons - in a cocktail of sex, drugs and violence reminiscent of those private eye yarns you read in pulp fiction.

As if to emphasise the buddy buddy nature of their relationship, Kilmer recalls throwing an Oscar nomination party and seeing a post-rehab Downey there. "You look at his face and he's just happy he didn't die," he says.

"Every day was just so much fun to be with him. It's wonderful to see someone who's a lovable guy. There are mean people in our business, tortured characters or whatever, who do bad things. He didn't do anything bad to anybody, just to himself. He got arrested because he had too much fun.

"He had a lot of love and support in the community, and Hollywood does love a comeback. At Cannes, it was the longest ovation I'd ever heard. I was convinced after a couple of minutes they were happy he didn't die too." Kilmer too has encountered his share of problems with the Hollywood machine, although he's always done exactly what he's wanted. "I've been successful and fortunate to be able to make choices that aren't the correct ones and it hasn't mattered," he says.

"I say it hasn't mattered but this film is a comedy and I've been looking to do one for ten years because I turned down so many. There are rhythm rules in Hollywood - if you didn't just do a romantic lead with the right girl, then you can't do certain things.

"Every now and again you get lucky and I've been very lucky for a long time and, like Robert, been able to do different things and not be kicked out. It's a finnicky little club, they all like going to the same places on vacation and stuff.

'BUT I stopped doing the larger movies, partly because of my kids. The responsibility of doing press is more than ever. When I did the Prince of Egypt animated film, I gave over 3,000 interviews. Actors are happy to do it because it makes more money the better press they have.

"Now you spend months doing it. I got a little anxious I wasn't going to be present as a parent or do things that mattered to me."

He feels it's even harder on girls, who have to spend hours on picking the right dress for the premiere. It's easy to fall into responding to someone if they're on magazine covers all the time, but it's not a good thing. "Like Paris Hilton, she's famous for nothing. It's what we're celebrating in my country - the nothingness of her. It's funny, a reality show is her life. That's a very strange thing to consider."

Kilmer doesn't feel the need to work for the sake of it, taking time off after making five or six movies in a row. There were personal issues to be considered too as his marriage to British actress Joanne Whalley ended. "I found I was getting divorced on TV," he says. "We get along fine now. There were helicopters and phone taps, this crazy life like Angelina Jolie's going through now. There are things you don't want to have to consider, like being concerned how she looks when she goes to buy toothpaste because of photographers."

He was in London this summer starring on the West End stage in the steamy drama The Postman Always Rings Twice. Before that, he played Moses in a musical version of The Ten Commandments on Broadway, a choice that made his agent cry.

"Maybe I would change my philosophy if I couldn't feed my family. So far I've been able to do things that were challenging for me personally and consistently made money for my employers," he says. "Someone told me the other day that I'd made $1bn for my employers. That's something special because I've been independent."

That even extended to taking third billing - although it was behind Robert De Niro and Al Pacino - in the thriller Heat. "My agent laughed at me," he recalls. "But Batman was a big success and the director Michael Mann is a good businessman and put me on the posters for Heat."

He points out that between them he and Downey have been making movies for 50 years. Downey's well-publicised drug problems very nearly killed him, let alone his career which had seen him Oscar-nominated for his portrayal of Charlie Chaplin in Richard Attenborough's biopic Chaplin.

DOWNEY enters the room, a coffee in his hand and a cigarette on his lip, showing that caffeine and nicotine are his drugs of choice now. He should have been on his honeymoon, having married Kiss Kiss Bang Bang's executive producer Susan Levin the previous week. A few days in the South of France is all they've managed.

The script first came to his attention when he heard her "laughing her arse off" while reading it. Intended as a project for Johnny Knoxville, it eventually came to Downey and it's impossible to think of anyone playing it better.

He became deep into martial arts while making the movie, more for himself than to prepare for the action scenes. "I would have my guy on set every day of the shoot. Everyone would break for lunch and I would have my kung fu guy training me," he says. "I can defend myself against practically anybody, as opposed to actually hurting anybody."

He has another five or six movies awaiting release or in production, almost as though he's trying to make up for lost time. "I can't really figure it out, I think it's what it always was. I'd read a script that I hated and go do it. Then I'd go, 'that was what I expected, I knew it wasn't going to be any good'," he says.

"I just happened to get a lot of really cool offers, probably twice as many as I did all in this period of time. It's also probable that in the next year or 18 months I'm the best deal in Hollywood. It's like buying a used Lotus for a few hundred pounds and I'm happy to be on the road again."

There have been disappointments, including the film version of Dennis Potter's TV hit The Singing Detective, with Downey in the role Michael Gambon played in the BBC original. "The thing is not to hold on to defeats - for lack of a better word - you spend a lot of time and energy on them," he says.

l Kiss Kiss Bang Bang (15) opens in cinemas on Friday.