LONDON - Britain's King Charles handed over a senior military role to his son Prince William at a ceremony on Monday, marking a rare joint appearance for the pair as the king steps up his return to public duties after his cancer diagnosis.

Charles presented William with the title of Colonel-in-Chief of the Army Air Corps, a position the 75-year-old monarch held for 32 years, in front of an Apache helicopter, and watched by service personnel at the Army Flying Museum in southern England.

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"He's a very good pilot indeed," Charles said of his son, a former helicopter search and rescue pilot for Britain's Royal Air Force.

The visit was Charles' latest engagement since he returned to work at the end of April, almost three months after Buckingham Palace announced he was being treated for an unspecified type of cancer.

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William, 41, had also taken a break from official duties for several weeks in March and April this year, choosing to spend time with and care for his wife after she revealed she was undergoing preventative chemotherapy for cancer. He said on Friday she was "doing well".

At the handover ceremony, Charles said he was saying goodbye with "sadness" but the Army Air Corps would go from "strength to strength" under his son.

"Look after yourselves and I can't tell you how proud it has made me to have been involved with you all this time," Charles said.

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The title transfer was announced last August after Charles' accession to the throne. William spent time with the Corps, viewing training, equipment and hearing from soldiers later on Monday.