Our real challenge is to get to the people who are the hardest to help

Prince Charles

"The most important thing is to keep looking at where we need to do the most work, the bits where people drop through the nets that exist," he told the BBC.

"Our real challenge is to get to the people who are the hardest to help."

Prince Charles said he was proud the trust was still doing what it set out to achieve.

"When it first started it was such a small operation it was one or two people and a dog in a shed practically," he said.

"Now it's got so huge."

Begging letters

Millions of pounds have been raised for the trust's volunteer programmes, study grants, business loans and confidence-building projects.

The trust now employs about 500 people, has about 8,000 volunteers and helps thousands of young people each year.

Music to royal ears. The prince is pleased with the trust's success

The prince said he was still involved in the trust's day-to-day work.

"I spend my life writing letters to goodness knows who asking for money," he said.

Celebrities who had helped support the project were thanked at a party thrown by the prince and his long-term companion Camilla Parker Bowles at St James' Palace on Monday.

Stars at the event included singers Mick Jagger, Sir Elton John and Geri Halliwell as well as actress Joanna Lumley.

Young people taking part in trust projects said they have noticed the difference in themselves.

Life-changing

Matthew Doughty, taking part in a personal development course at a nursery school in Birmingham, said the project had given him confidence.

"I used to be really quiet. I never used to talk to people face to face," he said.

"But coming on this course has changed me."

On Tuesday Prince Charles opened a shelter for homeless people in Lambeth, south London, in partnership with the charity Centrepoint, which inspired him to start the trust in 1976.

The prince insists the trust's work will continue with the same enthusiasm.

But he said he did not know whether his sons, William or Harry, would follow in their father's footsteps at the helm.

"Eventually I hope my children will take an interest in it.

"William may want to start something of his own depending on what circumstances he finds himself in at the time."