Overview
For more than four decades, the British state ran undercover police officers — operating under false identities — inside hundreds of domestic political groups, environmental campaigns, trade unions, and social justice organisations. The programme was coordinated primarily through the Special Demonstration Squad (SDS), established within the Metropolitan Police in 1968, and later the National Public Order Intelligence Unit (NPOIU). Both units operated with oversight from and in collaboration with MI5.
The operation became public in October 2010 when the Guardian revealed that Metropolitan Police officer Mark Kennedy had lived undercover for seven years as environmental activist “Mark Stone,” participating in direct actions across Europe, forming a long-term sexual relationship with a female activist, and feeding intelligence to police forces in at least twenty-two countries.
Scale and Methods
The SDS ran continuously from 1968 to 2008. Officers were given entirely new identities — often based on the names of deceased children, a practice later described by the public inquiry as causing “profound distress” to bereaved families. Deployments typically lasted four to five years. Officers embedded themselves in organisations ranging from socialist and anarchist groups to anti-racist campaigns including those monitoring the investigation into the murder of Stephen Lawrence.
At least fifteen undercover officers have been confirmed to have had sexual relationships with the women they were spying on — relationships the women had no knowledge were false. In 2015, the Metropolitan Police issued a formal apology to the women deceived. Eight women received financial settlements.
MI5 Connection
While the SDS was nominally a police unit, declassified documents and testimony before the Undercover Policing Inquiry (established 2015, chaired by Sir John Mitting) confirmed regular intelligence-sharing between the SDS and MI5’s domestic counter-subversion section. MI5 requested information on specific targets and in some cases directed surveillance priorities. The precise extent of MI5’s operational control remains subject to ongoing inquiry hearings, with significant portions of evidence heard in closed session due to national security claims.
Political Targets
Groups confirmed to have been infiltrated include: the Socialist Workers Party, Class War, the Militant Tendency, the Green Party, animal rights organisations, anti-fascist groups, and the family justice campaign of Doreen Lawrence (mother of Stephen Lawrence). The inquiry has confirmed infiltration of over one thousand organisations to date, with officers using stolen identities of deceased children as their cover personas.
Inquiry and Accountability
The statutory public inquiry, formally titled the Undercover Policing Inquiry, began hearings in 2020. As of 2025, it continues. Hundreds of victims have been granted “core participant” status. The inquiry has confirmed the practices were systematic rather than the result of rogue individuals. No criminal charges have been brought against any officer or MI5 official in connection with the programme.