Britain's Prince William has finished a three-week attachment with the country's security services, Kensington Palace said Sunday.

The Duke of Cambridge spent time at the domestic intelligence service MI5, foreign intelligence MI6 and the cybersecurity agency GCHQ.

"Spending time inside our security and intelligence agencies, understanding more about the vital contribution they make to our national security, was a truly humbling experience," William said.

"These agencies are full of people from everyday backgrounds doing the most extraordinary work to keep us safe."

David, the only name given for GCHQ's head of counterterrorism operations, said William had worked "exceptionally hard to embed himself in the team."

William spent more than seven years in the British military after graduating from university in 2005.

The 36-year-old is second-in-line to the throne, after his father, Prince Charles.

amp/jm (Reuters, AFP)

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