Schoolchildren will be on their best behaviour when the Queen and the Duke of Edinburgh pop in for a spot of lunch.

The royal guests will be in Horsham tomorrow and the first stop will be Christ's Hospital School at 11.45am.

While enjoying a tour of the historic site, they will be joined by the Duke and Duchess of Gloucester for lunch with about 300 pupils aged 11 to 18, teachers and other guests.

The visit has been organised to mark the 450th anniversary of Edward VI granting the school a royal charter in recognition of its charitable work.

Since then, the school has enjoyed a close relationship with the Royal Family. Queen Victoria was a governor.

Headteacher Dr Peter Southern said: "It is a great honour for us to receive the Queen and the Duke of Edinburgh and the Duke and Duchess of Gloucester.

"The pupils, staff and trustees are looking forward to welcoming them and providing a glimpse of the very special opportunities given to children from all walks of life at Christ's Hospital."

The royal entourage, minus the Duke and Duchess of Gloucester, who will remain at the school to open a refurbished boarding house, will then leave for the town centre where they will unveil a bronze sun dial at 2.45pm to mark the end of a multi-million-pound development project.

District council chairwoman Vivien Lyth said: "It's a very exciting time for Horsham. It's been 25 years of development coming to fruition and we are absolutely delighted and honoured they will be joining us."

The royal couple's tour will end with a visit to the newly-built Capitol Arts Centre at 3.10pm where they will see a musical performance by Horsham Children's Choir and unveil a plaque.

Jill Shuker, director of the Samaritans for Horsham and Crawley, will be among the throng to greet the Queen. She said: "I wouldn't say I'm nervous - just excited."