Jenny Bond, the BBC's royal correspondent, has trailed many a royal visitor round various healthcare establishments. She believes the visits are useful. 'I have seen it all around the world,' she says. 'After they leave, the staff and patients' day is brightened and their spirits lifted.

'I was with Prince Charles when he visited a clinic in the Balkans and after he had left, the clinic staff threw their arms round each other and shrieked with joy. It sounds trite but when a royal visit is over there are a lot of smiling faces left behind.'

Public relations consultant Max Clifford says: 'It's difficult to put a value on having a royal as a patron or visitor. Princess Diana had huge earning potential. She was the star of the royal family in terms of fundraising and awareness. After her there is a long gap. It is certainly still a plus having a royal as a patron or visitor but nothing like it used to be, except perhaps with older people who are more interested in the royal family.'