The Prince of Wales returned to RAF Cranwell, where he trained to become a pilot, and spoke to officers at their graduation. Princess Diana’s sister, Lady Sarah McCorquodale, also joined William at the ceremony.

Prince William at RAF Cranwell, Lincolnshire. Pic: PA

Prince William has told RAF officers the UK will be relying on them to deal with “future threats” during what he called a “time of change and uncertainty”.

The Prince of Wales spoke at a graduation ceremony for more than 50 officers who have completed their training at the Royal Air Force College Cranwell in Lincolnshire.

William was also joined by his mother’s sister Lady Sarah McCorquodale – an unusual appearance since members of the Spencer family do not normally attend royal engagements.

The prince trained at RAF Cranwell, where he flew solo for the first time and later received his wings from his father during a ceremony there in 2008.

He remained in the RAF for much of his active military career, going on to fly as a helicopter pilot.

In his speech to officers, William said: “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.”

During the graduation, where he was representing his father at the Sovereign’s Parade, he acknowledged the royal salute of the officers who spent up to 24 weeks undergoing strenuous military training.

The prince, who wore his RAF uniform and was still sporting his summer beard first seen in August, spoke about the roles the officers will play “in supporting the futures of your countries’ air forces”.

“I say ‘your countries’, as I know that in addition to our newest Royal Air Force officers on parade today, there are also officers from Jordan, Kenya, Pakistan and Uganda,” he said.

“Multi-national relationships are key to international defence, security, and peace.”

Last month Lady Sarah – one of Diana, Princess of Wales’, siblings – attended the funeral of the late husband of her sister Lady Jane Fellowes.

William and his estranged brother the Duke of Sussex also attended the service but did not talk to each other, according to reports.

Earlier in the week William spoke about his previous military career and love of helicopters.

As patron of Wales Air Ambulance, he visited the charity’s headquarters in Llanelli in honour of Air Ambulance Week.

The former RAF search and rescue pilot also served with the East Anglian Air Ambulance from 2015 to 2017.