Sophie, 17, is a member of Youth Cable TV, a West London project which offers young people from disadvantaged urban areas the chance to learn film and television production skills in a studio setting. Programmes made by YCTV are broadcast on a London cable network.

Project director Sabrina Guinness met Ford at a New York dinner party last year and told him about YCTV. She didn’t ask for a donation and that, she thought, was that. Until last month, when he telephoned the studio to say not only would he like to donate the proceeds from the premiere of his latest blockbuster to the studio, but he could visit and offer the young production crew an exclusive interview.

Sadly, the premiere of Ford’s new film, Airforce One, was due to take place last Thursday but was cancelled after the death of Diana, Princess of Wales. However, the film’s production company, Buena Vista, has agreed to donate the amount expected to have been raised on the night.

“It was just the most fantastic surprise. Harrison didn’t have to do this, but his belief is that practical experience is as good a way to learn as standard academic education,” said Ms Guinness.

YCTV offers training in anything from editing to camera work, vision mixing to presenting. The hope is that with this experience those young people aiming for a career in the highly competitive media world will have an extra edge.

Sophie Thomas, who is due to start an intermediate course in art and design at Westminster College, said: “Doing this has got me into college. I was able to produce a video portfolio of all the stuff I’ve done here, which the admission tutors at Westminster said they were really impressed by. Last year I got a distinction in some GCSE coursework by using the facilities here to do a really professional job.”

Movie star visits aside, Sabrina Guinness is hoping to expand YCTV into schools. She said: “Most of our current members are referrals from local outreach workers or the Prince’s Trust, but I’m also trying to encourage teachers to use us. The number of pupils taking media studies goes up every year. Where are they all going to get their practical experience from? Very few schools have the kind of equipment and facilities we do for practical coursework. We could offer schools our space and expertise.”

During Ford’s visit, the YCTV crew insisted the Indiana Jones star fill out a membership card before they showed him how to use the equipment. “They were pretty sassy with him, I must say,” said Ms Guinness.

As the star watched the filming of YCTV’s regular DIY show and saw the presenters trying to sand down a table, he couldn’t resist taking over and showing how it was really done.

Typical Hollywood prima donna behaviour, then? “Well, he was once a carpenter, so he knew what he was doing”, said Sophie, “although he told me acting was easier. I want to be a scriptwriter - who knows, he might be in one of my films one day”