The military’s most secretive unit is on a recruitment drive to select more men and women to carry out undercover operations, The Telegraph revealed.

The Defence Human Intelligence Unit (DHU), also known as Defence Humint Unit, works closely with the Special Forces.

The unit’s role is to obtain “human intelligence” for use by the British Armed Forces by creating a network of civilian agents in war zones, such as in Iraq, Syria and Afghanistan.

The DHU is currently deployed on operations around the world, working with the UK Special Forces, MI5 and friendly foreign nations.

But like many specialist organisations within the military, the DHU is struggling to recruit enough military personnel, in part because of the shrinking size of the Armed Forces.

The Royal Navy and the RAF are both understrength and three weeks ago The Telegraph revealed that the Special Boat Service (SBS) and the Special Air Service Regiment (SAS) have also faced a recruitment crisis caused by a shortage of suitable personnel.

A senior defence source told National Security News: “The DHU recruits across all three services and is finding it difficult to recruit enough men and women with the appropriate skill set. The unit needs people who are very fit and motivated. They must also have a very persuasive personality because they need to convince people to undertake some very dangerous tasks. The work is very stressful but very rewarding.”

Some of the organisation’s operators are also trained interrogators and have managed to obtain crucial and timely intelligence from captured enemy personnel that sources say has helped to save the lives of dozens of British personnel.

But the role is not without risk: since the formation of the organisation in the early 2000s, six operators have been killed on operations and several more have been wounded, although none of the deaths were publicly attributed to the unit.

The DHU is now actively recruiting new personnel within the Armed Forces and the selection course is open to troops above the rank of colour sergeant, or the equivalent in the Royal Navy and RAF, and irrespective of sex.

Physically fit and mentally agile

The recruitment, selection and deployment of agent handlers is known within the military as Op Samson and all of its activities are classified as secret.

Any service person interested has to apply to attend a briefing day and if regarded as being potentially suitable they will be offered a place on a selection course.

A Ministry of Defence (MoD) document seen by National Security News gave brief details of the role.

The document said: “As an agent handler you will be deployed and responsible for running and recruiting of sources from the local population, in order to covertly infiltrate organisations and areas of interest.

“You will direct, manage and train sources in order to gather intelligence, without compromise. You must be physically fit and mentally agile.”

The selection and training of interrogators, which is also run by the DHU, is called OP Metis.

The MoD document added: “As an interrogator (OP Metis) you will be part of Defence’s contingency capability for debriefing and interrogation operations worldwide tasked with turning unwilling subjects into willing allies. In the UK you will be employed on the UK’s Defence Debriefing Team with which you will deploy across the UK liaising with national agencies and debrief a broad range of subjects on defence issues.”