Instead of marrying his fiancée in Windsor's Guildhall on Friday, Charles will now travel to Rome to pay his respects at the Pontiff's burial.
The heir to the British throne decided to delay his nuptials until Saturday in order to represent the Queen at the service. Paddy Harverson, Charles's communications secretary, said the Prince felt that switching the date was "absolutely the right thing to do".
Camilla will not be accompanying Charles to the funeral.
The bride and groom-to-be yesterday attended the sombre Vespers for the Dead service in London's Westminster Cathedral in honour of Pope John Paul II.
Charles, wearing a navy blue suit and black tie, made no comment as he arrived with Camilla, who was dressed in a black skirt and jacket, high heels, hat and gloves.
Mrs Parker Bowles took her seat in the Cathedral next to British Prime Minister Tony Blair.
As Charles sat, he knelt forward to pray bringing his hands to his head.
Charles's quest to marry Camilla has been dogged with setbacks since their engagement was announced in February.
Queen Elizabeth's decision to stay away from the civil ceremony, the row over whether Mrs Parker Bowles would ever be known as Queen Camilla and the change in venues from Windsor Castle to the local town hall have all featured in the long list of problems the Prince has faced.
Now royal staff will be hurrying to notify all the 750 guests attending the blessing afterwards in Castle's St George's Chapel of the change in plan.
Invitations for the wedding will now contain incorrect information, although a royal spokesperson said the admittance cards would still be valid.
The event placed Mr Blair, whose wife Cherie is a Roman Catholic, and the Archbishop of Canterbury Rowan Williams, who was due to perform the blessing at Windsor on Friday, in a difficult position.
Mr Blair's official spokesman said: "I think Clarence House were very well aware of the significance of the Pope's funeral and therefore that was part of their decision-making process." But he stressed: "The decision was one for them and they alone to reach. The Prime Minister is now very glad he is able to go to both events."
It is thought the 20-minute civil ceremony will take place on Saturday morning ahead of other scheduled weddings and prior to the start of the Grand National at Aintree, where a couple of the runners have royal-inspired names.
Memorabilia produced for the big day was being hastily scrapped and reissued with the correct date, although some royal fans were keen to get the 'old' souvenirs with Friday's date on them in case they become collectors' items.
Commemorative coins marking the Prince of Wales's wedding were among the items having to be rapidly remodelled.
The Royal Mint released images showing the original date '8th April 2005' printed on the reverse under the Prince's feathers.
A spokeswoman for the Royal Mint said: "The presses were due to run but we're now having to switch the date."
Mr Harverson said the Prince very much wanted to go to the funeral.
"He had a lot of respect for the Pope," he said. "He feels this is absolutely the right thing to do. Mrs Parker Bowles agrees entirely.
"Hopefully the majority of guests that were going on Friday will be there on Saturday."
The news of the postponement of the wedding sent businesses in Windsor into a spin.
Management at the Harte & Garter Hotel, which has hired out a series of front-facing rooms with balconies overlooking Windsor Castle and the Guildhall for the world's media to use, went into closed meetings within minutes of the official announcement.
Further up the hill at The Castle Hotel, which stands just metres from the spot where Charles and Camilla will now tie the knot on Saturday, the picture was the same.
Bookmakers claimed they face the biggest pay out in Grand National history if hotly fancied Clan Royal wins at Aintree as the Prince of Wales marries Mrs Parker Bowles.
Leading bookmakers said they are now concerned about a repeat of the famous "coincidence" win in 1992, when the heavily backed Party Politics won in an election year.
Current 10-1 joint third favourite Clan Royal and Royal Auclair, a 25-1 shot, could also follow in the hoofsteps of Royal Mark, which won at Wolverhampton on the wedding day of Princess Anne and Captain Mark Phillips in 1973.