PRINCE Charles will be joined by his companion Camilla Parker-Bowles during his visit to Marlborough tomorrow, it was revealed this week.

The prince's press office at Clarence House said it was not unusual for Mrs Parker-Bowles to join him on formal engagements and she had been with him on a number recently.

Mrs Parker-Bowles, whose home is at Reybridge, near Lacock, will be in Marlborough in her capacity as a trustee of the Bobby Van Trust.

Wiltshire has two Bobby Vans whose operators, Alan Weston and Rod Law, attend homes of crime victims and advise them on security.

Both men and their vans will be in the High Street near the Merchant's House during the royal visit. Mrs Parker-Bowles will make her way separately to the Merchant's House where she will join Prince Charles for a tour of the 17th century building that is under restoration by a local trust.

The couple will then emerge on to the street to view the two Bobby Vans. That is the only part of the prince's visit where Mrs Parker-Bowles will accompany him, said his press office.

Prince Charles, whose visit is the highlight of the town's celebrations of the granting of its charter by King John 800 years ago, will arrive at the Marlborough College by helicopter at 10.45am.

He will unveil a plaque at the public school on the spot where King John would have stayed in the town's former castle. He will also have an opportunity to chat with teachers and pupils.

At the college he will be introduced to Marlborough Mayor Graham Francis and the visiting mayor and mayoress from Marlborough, Massachusetts USA, Dennis and Cheryl Hunt, who have been invited across the Atlantic for the festivities.

At about 11.30am, Prince Charles will be escorted by Coun Francis along the High Street where he will take in the architecture, said Clarence House.

It's expected that, at about 11.50am, the prince will walk behind Waitrose to compare the design of its new extension with neighbouring historic buildings. The royal party will return to the High Street by walking through the store where the prince will have a brief opportunity chat with some of the staff.

Once back in the High Street the royal walkabout will continue and the prince will be met by groups from local schools and organisations.

He's due to arrive at the Merchant's House at around 12.15pm for his tour before viewing the Bobby Vans with Mrs Parker-Bowles at around 12.35pm.

At that point he will leave her and head for the town hall, where he will be welcomed by town crier Alfie Johnson at about 12.50pm, and unveil a plaque commemorating the anniversary.

The prince is expected to spend about 40 minutes in the town hall where he will meet invited representatives of local clubs, groups and organisations before taking his leave.

Mayor Graham Francis said yesterday: "Everything we can plan for has been planned for. Our biggest worry is the weather and whether this glorious period of sunshine we have been enjoying will hold for the royal visit and the weekend's events."