The National Domestic Extremism Unit is a national police unit within the Metropolitan Police Service Business Group.

Originally the unit was set-up within the operational arm of the Association of Chief Police Officers (England & Wales), specifically within TAM (Terrorism and Allied Matters) Committee. The unit reports to the ACPO committee and was answerable to all chief police officers across the country.^[1]

In November 2010 it was announced that the three ACPO units commanded by the National Coordinator for Domestic Extremism would be rebranded as the National Domestic Extremism Unit and brought under the control of the Metropolitan Police Business Group by mid-2011.^[2] The units were:

• National Extremism Tactical Co-ordination Unit
• National Public Order Intelligence Unit

As a result of The Guardian articles with regards the activities and accusations of PC Mark Kennedy of the National Public Order Intelligence Unit within the National Extremism Tactical Co-ordination Unit, and the collapse of the subsequent trial of six activists, a number of initiatives and changes were announced:^[3][4]

• Acknowledging that "something had gone very wrong" in the Kennedy case to the Home Affairs Select Committee,^[5] Home Office minister Nick Herbert stated that ACPO would lose control of three teams involved in tackling domestic extremism. Herbert re-announced the already planned transfer of the units to the Metropolitan Police, with acting commissioner Tim Godwin confirming that this would occur at the earliest possible timescale.^[3]
• Her Majesty's Inspectorate of Constabulary announced that Bernard Hogan-Howe would lead an investigation into ACPO, to assess whether undercover operations had been "authorised in accordance with law" and "proportionate".^[3]
• The Serious Organised Crime Agency announced an inquiry into the conduct of Mark Kennedy.^[3]
• The Independent Police Complaints Commission announced an investigation into Nottinghamshire Police, over allegations it suppressed surveillance tapes recorded by Kennedy, the contents of which may have exonerated the six Ratcliffe activists.^[3]

• National Coordinator for Domestic Extremism
• National Public Order Intelligence Unit
• National Extremism Tactical Co-ordination Unit
• National Domestic Extremism Team
• Special Demonstration Squad