Ms Williams says she will have her nerves under control

But the superintendent registrar of the Royal Borough of Windsor and Maidenhead also says she is "delighted and honoured".

Ms Williams, who has been marrying couples for over 10 years, says the marriage of Prince Charles to Camilla Parker Bowles on 8 April will be special - but they won't get any special treatment from her.

"[It won't be different] in terms of the way I treat my couples," she says. "Which is with respect, and to try to get their ceremonies correct for them."

But she admits that the "momentousness" of the occasion will make it different to any other ceremonies she has taken charge of.

"It's a one-off in my lifetime. It's a very special occasion indeed, to be part of history. I will be nervous probably, but I will have it under control."

Ms Williams, like both parties in the royal wedding, is divorced. She also has two daughters - Pippa, 19, and Charlotte, 22 - close to the ages of Princes William and Harry.

But she won't be drawn on whether the similarities in their family situations will influence her treatment of the royal couple.

The wedding is due to take place at Windsor's Guildhall.