The Duke of Cambridge asked personally for a chance to experience first-hand the challenges faced by MI5, MI6 and GCHQ as they fight to protect our realm. As Britain remains on "severe" terror alert, the second-in-line to the throne spent some of his time "on the streets" engaged in intelligence gathering operations. Intelligence experts last night hailed the news as a "unique event of the greatest importance".

Prince William was embedded to each service for a week.

While he was able to return home to his wife Kate and three children during his secondment with the Secret Intelligence Service (MI6) and The Security Service (MI5), during the first fortnight, he opted to stay overnight at GCHQ's sprawling base in Cheltenham last week.

Intelligence officers were asked to simply address him as "Will".

As a member of the Privy Council he was not forced to sign the Official Secrets Act. But he was nevertheless instructed not to discuss details of his assignments with the Duchess of Cambridge.

Speaking about the experience he said: "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. These agencies are full of people from everyday backgrounds doing the most extraordinary work to keep us safe.