Miss Middleton, 29, was confirmed on March 10 at St James’s Palace at a service presided over by the Bishop of London, the Rt Rev Richard Chartres.

According to reports, the decision to be confirmed reflects Miss Middleton’s “personal journey” of faith.

According to a spokesman for St James’s Palace, Miss Middleton’s family and Prince William were in attendance at the service.

“Miss Middleton, who was already baptised, decided to be confirmed as part of her marriage preparations,” the spokesman said.

Bishop Chartres has reportedly counselled Miss Middleton ahead of the wedding on April 29, at which he will deliver the sermon.

The bishop is a close personal friend of Prince Charles and counselled Prince William after the death of his mother, Princess Diana, in a car crash in 1997.

A prayer for Prince William and Miss Middleton has been released by the Church of England ahead of the wedding.

It asks God to “look with favour” on the couple and all those “made one in marriage”.

The prayer also asks God to help Prince William and Miss Middleton keep the promises they will make to each other on their wedding day and “continue in lifelong faithfulness to each other”.