Earl Spencer's moving eulogy at his sister Diana's funeral was watched by 2.5 billion people around the world and is regularly cited as one of the greatest speeches of the 20th century.

This, combined with his role coaching the business community world wide, makes him an ideal candidate to mentor the talented young public speaking hopefuls in BBC Two's The Speaker.

"I became involved with The Speaker because I thought the idea behind the series was so good," says Earl Spencer. "I'm the father of four teenagers, and I was keen to be part of a programme that celebrated young people and their talents, rather than criticised them - which is what we all read and hear far too much of in the mainstream media."

The Earl's role was to mentor the contestants in the art of communicating information with his family's ancestral seat, Althorp in Northamptonshire, used as an integral part of the proceedings. "My remit was to teach the contestants how to deliver information," he explains. "Each of the participants was taught the art of tour-guiding and given one of the rooms that is open to the public at Althorp in which to perform as a guide. Information-giving is a key component of public speaking and transmitting true facts, in digestible form, is crucial if you want to be not only believed, but listened to with interest."

Earl Spencer was impressed by the quality of the eight contestants left in the competition at this stage. "They were, frankly, fantastic," he says. "They had a buzz, a sharpness and an energy about them. Each had clear gifts, and I think people who worry that a programme about speech-making may sound a little worthy and highbrow will be amazed by what they see - the teens are fascinating, and really hook you in."

The Earl, who made his first speech at the age of four when he opened a public hall in Northamptonshire, adds: "Great speakers have a natural gift, but I believe that anybody can become good at public speaking. I coach high-flying business people on presentational skills, and I have seen even the most nervous, confusing and confused clients become good at it - which is just as well, since very few poor speakers can survive in the top echelons of business."

Renowned as a great public speaker himself, which public-speaking figures inspire the Earl? "I love the speeches of Bobby Kennedy," he says. "JFK, of course, grabbed most attention. But his brother matched him for charm and charisma while also, I believe, having more sincerity about him. His words were heartfelt and often beautiful."