Prince William supported by Princess Diana's sister as royal warns of 'challenges ahead'

The Prince of Wales, 42, appeared at the graduation on behalf of his father King Charles.

It is understood Lady Sarah was in the area and wanted to support Prince William.

Video footage from the event showed Lady Sarah in the background while Prince William chatted at a reception after the parade.

Prince William referenced his own training at RAF Cranwell in a speech: "Whilst I didn’t graduate on this exact Parade Ground, I did graduate from flying training here, so I know something about the celebrations that will come later — so I promise I’ll only take a few minutes of your time!"

The Prince of Wales, who earned his wings at RAF Cranwell in 2008, said the force had “a distinctive character, spirit, and attitude” that enabled its officers to pull together, “no matter the challenge or environment”.

He added: “We live in a time of change and uncertainty, and you, as the future of the Royal Air Force, are the ones who will ensure that we are able to adapt and face future threats.

"To the families and friends gathered here — thank you for your encouragement and understanding to get these brilliant men and women this far, and for the empathy, compromise and dedication that will be required to give these officers every chance of success in their careers."

Princess Kate, King Charles, Queen Camilla and Lady Sarah all attended Prince William's graduation from RAF Cranwell in 2008.

Sarah is the late Princess Diana's eldest sister, and does not live far from RAF Cranwell.

Her life is outside the spotlight, however, Sarah and her siblings have stepped out to support Prince William and Prince Harry many times.

Lady Sarah and Lady Jane Fellowes, 67, were present when William and Harry unveiled Diana's memorial statue at Kensington Palace on what would have been her 60th birthday in July 2021.

In addition, they all came together recently at the memorial service for Jane's late husband, Lord Robert Fellowes.

Lord Robert, who served as Queen Elizabeth's private secretary from 1990 to 1999, died on July 29 at age 82 of undisclosed causes, and was honoured at a private service in Norfolk one month later.

Prince Harry's unexpected transatlantic travel to pay his respects was deeply emotional, leaving him "pleased" and guests "astounded," a source claimed.

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The trip came just two days ahead of the anniversary of Princess Diana's death.

However, Harry's surprise arrival in the UK did not lead to a public reconciliation with his brother, William, amid their ongoing rift.

At the service at St Mary’s Church, the estranged brothers sat apart, each with different groups of their maternal cousins.

The Duke of Sussex stayed with his uncle Charles, the 9th Earl Spencer, at Althorp House following his surprise appearance at the memorial service.