Director Terry Gilliam choked up as he admitted it was "hard work" promoting The Imaginarium of Doctor Parnassus in the memory of its late star, Heath Ledger.

Ledger died of an accidental overdose while making the film, and his part was later finished by Johnny Depp, Colin Farrell and Jude Law.

At the world premiere in London's Leicester Square, Gilliam said of promoting the film: "It's hard work but it's worth it.

"It's hard when you start thinking back," he said.

"What's nice is the reactions of the people, it's not like I have to sell some turkeys, and Heath's performance is wonderful and Johnny, Colin and Jude saved the day. In a sense it's promoting itself," he added.

Praising the performances of the three actors, who all donated their fee to Ledger's daughter Matilda, Gilliam said: "They carried on the spirit of what Heath was doing. Colin swore he was channelling Heath at one point. Heath has a very powerful spirit."

He then joked he was angry Ledger was not there for the premiere. He said: "I don't know where he is tonight be he's beginning to p me off. We've got the film, where are you?"

Model and actress Lily Cole, who wore a full-length tiered Chanel dress adorned with jewels and shells, said she was pleased with how the film was completed after Ledger's death.

"I feel extremely proud of how everyone managed to finish it (despite) such a huge obstacle. I feel really honoured we managed to take all the energy Heath put into it and show it so people can see it. At the same time I obviously still feel sad."

Actor Andrew Garfield said of his co-star Ledger: "I have mixed feelings. I feel really happy his work is being seen because it's phenomenal.

"It's emotional, when you lose someone ... it's the worst feeling in the world.

"(Heath's) approach to things was fearless. He was always real and honest, it's ridiculous he isn't here anymore."

Also at the premiere were fellow cast members Paloma Faith, musician Tom Waits and Verne Troyer. Guests included Michael Jackson's sister La Toya, presenter Terry Christian and actor Peter Capaldi.

The film is in cinemas from October 16.