The Queen will join the Duke of Edinburgh at Westminster Abbey on Thursday to mark the 60th anniversary of the project which bears his name.
Paralympic gold medallist Hannah Cockroft and comedian Jon Culshaw are due to take part in the service in front of a 2,000-strong congregation to celebrate the Duke of Edinburgh's Award.
The youth achievement programme, which allows participants to win bronze, silver and gold awards, was launched in 1956, inspired by Philip's Gordonstoun school.
Over the past 60 years, more than 5.6 million young people have started the programme, and almost 2.5 million have achieved awards.
In a foreword for the service, the Duke of Edinburgh said: "The growth of the scheme owes everything to the untold numbers of volunteers who have given their time and enthusiasm to bring its benefits to a constantly growing number of young people all over the world."