Prince Harry and Prince William’s relationship shows no signs of improving (Image: Getty)

Prince Harry declined his ‘save the date’ invitation to the Duke of Westminster’s wedding after discovering his brother Prince William was set to take a leading role, it has been claimed.

The Prince of Wales is set to be an usher at the wedding of Hugh Grosvenor and Olivia Henson at Chester Cathedral, which will take place on June 7.

Sources claim that by bringing William into the bosom of the event, Prince Harry is said to have felt sidelined and so declined the invitation.

“William was asked to take up a leading role in the wedding and that’s what triggered Harry to decline an invitation. It was the final nail in the coffin,” the source told Express.co.uk. “Harry was very close to Hugh growing up so everyone thought it would have been him taking up a leading role, not William.”

It was first revealed in December that Prince Harry was not attending the wedding, which has been dubbed a ‘Royal wedding in all but name’, thanks to its high-level of expected Royal attendance.

Last year there was initial speculation that Prince Harry had been ‘snubbed’ from the event, but a source close to the Sussexes was at pains to explain to US publication Page Six that both Meghan and Harry had in fact received invites but had jointly decided to decline.

While the statement ended speculation that Hugh’s wedding would see the brothers reunited face-to-face for the first time since the Princess of Wales’s cancer diagnosis, it prompted a friend to say it was ‘incredibly sad it has come to this’.

Harry was said to have called the Duke himself to apologise for any inconvenience at him having to refuse but his true reasons remained a mystery, aside from the obvious ‘awkwardness’ with his family.

“Hugh and Harry were very close so it’s all so sad,” the source said. “Harry was at Hugh’s 21st birthday party and also went travelling with him to Africa. He’s also a lot closer in age to Harry whereas William is eight or nine years older.

“When they were growing up Harry and Hugh were much closer. Hugh was a young boy when William was in his late teens and early twenties. That’s why this has all come as such a shock.”

King Charles and Queen Camilla may make a surprise appearance at the wedding (Image: Getty)

A source claimed recently that Catherine’s name has not yet formally been removed from the guest list – which was put together last year, long before Catherine became aware she was ill – but warned that her name remaining on the list does not guarantee her attendance.

“William and Kate are both on the guest list and there has been no declining her invitation. But that might be because they have spoken informally. A lot is still up in the air with the Wales family,” the source said.

Catherine is well known to politely decline weddings, where possible, to avoid upstaging the bride.

Aides say that, with Catherine unwell, nothing at all in the Wales’s calendar is nailed-on. However, William’s decision to leave her side and visit to the Isles of Scilly recently was seen as a small sign that she may be doing better.

On February 27, Prince William pulled out of a memorial at St George’s Chapel Windsor at the last minute due to an undisclosed ‘personal matter’, even though his name was on the order of service. Three weeks later, Catherine released a video statement telling the world she was undergoing preventative treatment for an undisclosed form of cancer.

Kate and William’s 10-year-old son Prince George, the Duke of Westminster’s godson, is also expected to take a role at the wedding.

The Duke of Westminster is also godfather to the Sussexes’ son, Prince Archie.

Known as ‘Huey-boy’ to Harry, the 33-year-old remains one of very few close friends of William and Harry’s who managed to maintain strong a line of communication with both sides.

The Duke – dubbed the most eligible man in Britain thanks to his £10 billion wealth – is also close to his godfather, Charles, and walked in the King’s coronation procession carrying Royal standards.

“It’s still not confirmed as to whether the King and Queen will attend the wedding,” the source said. “They have a very busy schedule lined up around that date so it will be a case of how the King feels on the day following a busy few days in France for the D-Day commemorations on June 6.”

The billionaire Duke is hosting the wedding reception at his 10,872-acre Eaton Hall estate in Cheshire where he and his bride Olivia plan to move as soon as they are married. They are said to be keen to start a family right away.

A friend of the couple said last night: “It means a lot to the couple to be getting married at Chester Cathedral, it is where they will be putting down roots for the future. They are making a conscious effort to involve local and regional suppliers in several aspects of their day. The couple are incredibly grateful for the support and messages of congratulations they have received, especially from people in the region.”

The Duke plans to run his family head office from London while Olivia intends to continue her career in the sustainable food sector from the North.

Family friend Emily Few Brown, who runs catering firm Spook London, an ‘ingredient-led’ catering company with sustainable credentials and an emphasis on growing and foraging its own food, is said to be lending a helping hand for the event.

“Chester Cathedral will be closed on June 6 for rehearsals and there will be a rehearsal dinner in the evening,” the source concludes. “The wedding on the 7^th will be very much about focusing on local produce and sustainability.

“Guests have been asked to make donations to the Westminster Foundation instead of handing out gifts and they [Hugh and Olivia] are trying to make it as low-key as it can possibly be.”

A spokesman for the Duke of Westminster declined to comment.

Three weeks later, Catherine released a video statement telling the world she was undergoing preventative treatment for an undisclosed form of cancer.