The MDP's primary responsibilities are to provide armed security and counter terrorism services to designated high-risk areas, as well as uniformed policing and limited investigative services to Ministry of Defence property, personnel, and installations throughout the United Kingdom.

The MDP underwent a significant restructuring as part of the coalition government's post-2010 austerity measures, and the Strategic Defence and Security Review.

[9] These earlier constabularies were formed as a result of the Special Constables Act 1923, although their histories can be traced back much further as watchmen.

Since January 2008, the MDP has also taken on the role of providing armed security at four gas terminals in the UK, part of the critical national infrastructure.

[12] In February 2015, the MDP deployed officers to GCHQ Cheltenham on a full-time basis;[13] this was in response to the 2014 increase to the UK threat level from international terrorism.

[14] MDP officers are attested as constables in one of the three jurisdictions of the United Kingdom: England & Wales, Scotland and Northern Ireland, but can exercise their powers in matters relating to the Ministry of Defence Estate throughout the United Kingdom, and additionally in the circumstances described below.

These set out the agreed working relationship between the MDP and other police forces; outlining, where necessary, areas of responsibility and accountability.

The protocols make provision for consultation and co-operation between the forces, with the aim of delivering the best policing on the ground.

In practice, most new entrants are initially posted to nuclear division; either at one of the two AWE establishments in South East England or one of the stations in Western Scotland.

MDP officers retain a full national mobility liability, and can be posted anywhere in the UK at any time.

The DPF functions in a similar fashion to a trade union, with membership being voluntary,[34] except that — like all UK police forces — officers do not have the right to take strike action.

These include: Aside from their personal body armour, PAVA incapacitation spray, batons and Hiatt speedcuffs, all MDP officers are trained to use firearms and about 90% are armed at any one time.

The marine support units are responsible for the waterborne security of His Majesty's Dockyards and HM Naval Bases.

The new 15m boats, which are replacing the existing vessels, have a crew of three (plus room for four more passengers), a top speed of 30 knots and are fitted with both ballistic protection and CCTV surveillance systems.

Officers deployed to Nuclear Division are trained in CBRN defence and to work in radiologically controlled environments.

MDP TFU is tasked with, and equipped to provide, an advanced firearms response capability at short notice to the Atomic Weapons Establishment.

[45] The MDP has been implementing Project Servator as a new effects-based policing tactic since 2016 to deter and detect criminal and terrorist activity, as well as to reassure the various communities they serve.

[46][47] Project Servator tactics provide a strategic approach to defending sites that the MDP protects and are part of the Force's drive to deploy resources efficiently and effectively within its Operational Policing Model.