A-LIST actors including Ewan McGregor are taking a fraction of the fees they can command in Hollywood to star in a low-budget film by a writer and a director who have never made a feature film before.

Every actor approached by Edward Blum and Aschlin Ditta, whose careers have been limited until now to Crimewatch reconstructions and television dramas, wanted to be involved with Scenes of a Sexual Nature. They included Sophie Okonedo, the Oscar-nominated Royal Shakespeare Company actress who starred in Dirty Pretty Things and Hotel Rwanda, Dame Eileen Atkins, whose films include Gosford Park and The Hours, and Adrian Lester, the Olivier award-winner.

The story traces seven relationships during one afternoon on Hampstead Heath, where filming was taking place yesterday. Each tale has a comic element, but a dark undertone in exploring fantasy and reality.

McGregor, Scotland’s most successful actor since Sean Connery, became an overnight sensation as the heroin addict in Trainspotting. He is reported to earn $8 million (£4.4 million) a film since making it in Hollywood in Star Wars.

During a break from a morning’s filming of Scenes of a Sexual Nature, he said: “It’s so brilliantly written.” He plays a man discussing with his longstanding gay partner whether to have children, a comic scene in which they discuss who would give up work.

Dame Eileen and Benjamin Whitrow, whose many films include Chaplin, play an elderly couple who meet on a park bench. Each has been visiting that bench for the past 50 years, once a week, dreaming of the teenager they met there 50 years ago. They were those teenagers, they realise.

Blum, 37, was taken aback at the enthusiasm of such high-calibre actors to be in his film: “They just came thick and fast. It was unbelievable. Ditta, also 37, who has written for various television shows, most recently a Channel Four comedy drama No Angels, said: “We are so blessed with this cast. We are getting these amazing performances.”

They have been friends since they were 12. They were at school together in Ely, Cambridgeshire. Both were avid filmgoers, with Woody Allen a particular hero. Blum had previously made television documentaries and dramas, such as the ITV drama The Bill, and reconstructions for Crimewatch UK. He also directed a short film, The Last Post, which was nominated for a Bafta in 1996.

He had taken part in an annual competition at the Cannes Film Festival, which gives budding film-makers two minutes to pitch a film idea to a panel. He beat 400 entrants with his synopsis for another film, Crimebusters, co-written with Ditta and which they also hope to film.

That win led to being introduced to Emma Style, a casting director who had worked on films such as Tea With Mussolini, starring Dame Judi Dench and Dame Maggie Smith. She read their script, loved it and introduced him to agents.

Scenes of a Sexual Nature is believed to have a budget of £500,000, raised from private investors. The whole process, from finishing the script in June to raising the money and attracting the cast, took less than six weeks, rather than years of development.

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