The Prince of Wales' wedding to Camilla Parker Bowles has been postponed until Saturday, to allow him to attend the Pope's funeral in Rome.
The couple had planned to wed on Friday in Windsor
The couple had intended to marry in Windsor on Friday, but changed their plans when the Vatican announced arrangements for the service.
Clarence House said the prince, but not Mrs Parker Bowles, would represent the Queen in Rome.
Following the decision, Downing Street confirmed Tony Blair would also attend.
The prime minister had also been invited to Prince Charles' wedding.
Clarence House said the postponement of the ceremony was "a mark of respect" for the pontiff.
The Prince's spokesman added: "It is expected that the arrangements will be largely the same as previously planned and more details will be announced as soon as possible."
Paddy Harverson, Prince Charles' communications secretary, said Mrs Parker Bowles had agreed with the prince that postponement was "absolutely the right thing to do".
"The wedding is still going to be a good day, but it has just been pushed back 24 hours," Mr Harverson added.
"Hopefully the majority of guests that were going on Friday will be there on Saturday."
Clarence House had earlier said the wedding plans would not be affected by events in Rome.
Prince Charles cut short his Swiss skiing holiday to attend the Vespers for the Dead service for the Pope at Westminster Cathedral on Monday evening.
Mrs Parker Bowles accompanied him, sitting next to Prime Minister Tony Blair, who had delayed calling a general election as a mark of respect for the pontiff.
During the service, the leader of the Catholic Church in England and Wales - Cardinal Cormac Murphy O'Connor - said Pope John Paul II would be remembered as "Pope Paul the Great".
Prince Charles and Mrs Parker Bowles plan to marry in a civil ceremony at Windsor's Guildhall, followed by a church blessing in St George's Chapel at Windsor Castle, which the Queen will attend.
Clarence House has announced the blessing will take place at 1430 BST.
Lloyd White, of Windsor and Maidenhead council, said: "We are happy to accommodate this alteration in the plans."
Three other weddings booked for the Guildhall on Saturday will not be disrupted, he added.
Grace Beesley, 33, from Windsor, who is marrying Fraser Moores, 34, in the Guildhall at 1400 BST on Saturday, said she was "very excited" by prospect of sharing her wedding day with Charles and Camilla.
The couple are likely to be the first married in the hall after the Royal couple.
Miss Beesley said: "We won't have to make any changes to our wedding - the registrar rang us this morning and told us that - so it will just be another dimension to the day and a bit more exciting."
Mr Moores said he expected Windsor to be busier as a result of the postponement, but added: "I don't care - bombs could fall from the sky and I'm looking forward to still getting married."
Charles's quest to marry Camilla has been dogged by setbacks since their engagement was announced in February.
They have included the Queen's decision to stay away from the civil ceremony, the row over whether Mrs Parker Bowles would ever be known as Queen and the change in venues from Windsor Castle to the local town hall.