Prince William secretly embedded in Britain's secret service

"We all owe them deep gratitude for the difficult and dangerous work they do," the Duke said of Britain's security services. Photo / Getty

The Duke of Cambridge has spent the past three weeks secretly embedded with Britain's spies, it can be revealed, as he sees first-hand how the security services are combating terrorism.

The Duke, who will one day be king, has been working with MI5, MI6 and GCHQ in an unprecedented secondment across the three security services, joining their staff full-time to learn more about how they are protecting the country.

While at MI5, the Duke worked with analysts and investigators monitoring Islamist terror cells, security sources told The Sunday Telegraph.

The Duke of Cambridge recently concluded a three week attachment to MI5, MI6, and @GCHQ, as the three security services continue their vital work both at home and abroad to keep our people and our allies’ safe. pic.twitter.com/vXFcsbFgk5

— The Duke and Duchess of Cambridge (@KensingtonRoyal) April 6, 2019

He is understood to have worked in the field as well as in the office, with the placement said to have been valuable for both him and the intelligence services.

Saying the experience had been "truly humbling", he emphasised:

"We all owe them deep gratitude for the difficult and dangerous work they do."

A spokesman said the Duke had been "keen to see first-hand the extraordinary work that staff across the Security and Intelligence Agencies do" at a time when the threat level for international terrorism in the UK had been classified as "severe" for five years.

The project, which saw him spend a consecutive week with each of the Secret Intelligence Service (SIS), the Security Service and GCHQ, can now be disclosed upon completion.

The Duke has been noticeably absent from royal duties for the three weeks, conducting two investitures at the request of his grandmother, the Queen, and attending one evening event with his father and brother.

Instead, the father-of-three has been based in the offices of the security services watching, learning and being trained on how they "keep our people and our allies safe".

His first week was spent at MI6 to learn in detail the reality of its network of spies and handlers tasked with gathering foreign intelligence to protect Britain.

A spokesman said the Duke had seen first-hand how staff at the service, made famous around the world by the fictional James Bond franchise, "identify and exploit opportunities as well as navigate risks to its national security, military effectiveness and economy from those who wish the UK harm".

The Duke has been noticeably absent from royal duties for three weeks, conducting two investitures at the request of the Queen, and attending one evening event with his father and brother. Photo / AP

He is likely to have taken part in training exercises for new recruits, in which they practice identifying which threats to investigate and mapping out how to do so.

The Duke's second week was spent with MI5, focused closely on how they run counter-terrorism investigations on home soil using "analysis and surveillance".

Security sources told The Sunday Telegraph that the Duke was given an overview of the powers the service has and the tools at their disposal when investigating alleged terrorism. He was said to have appreciated and enjoyed the week.

A third and final week was spent on assignment at GCHQ in Cheltenham, where he "spent time with those using cutting-edge technology, technical ingenuity and wide-ranging partnerships to identify, analyse and disrupt threats".

The project served as high-level work experience for the Duke, who will one day require deep knowledge of the UK's security services after he succeeds his grandmother and father to be king.

After news of the attachment was made public, the Duke 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.

"They work in secret, often not even able to tell their family and friends about the work they do or the stresses they face."They are driven by an unrivalled patriotism and dedication to upholding the values of this country.

"We all owe them deep gratitude for the difficult and dangerous work they do."

GCHQ's Head of Counter-Terrorism Operations, known only as David for security reasons, said:

"Having The Duke of Cambridge spend time with our teams was an incredible opportunity.

"William worked exceptionally hard to embed himself in the team and comfortably held his own amongst some highly skilled analysts and operators.

"His Royal Highness asked some probing questions and demonstrated a real grasp of our mission.

"This was a rare opportunity to expose, in detail, the technical ingenuity and problem-solving skills needed on a daily basis to help keep the UK safe."