Covert policing in the United Kingdom

Covert policing in the United Kingdom are the practices of the British police that are hidden to the public, usually employed in order that an officer can gather intelligence and approach an offender without prompting escape.
Covert policing role.
Most British police forces have formed a unit solely for covert policing operations. One of the forces that makes extensive use of surveillance-led policing is Greater London's Metropolitan Police. The Metropolitan Police unit was formerly a Specialist Operations designation devoted to covert policing, which was SO10. Since then, most of the Specialist Operations units have been disbanded or merged, giving way to SO10 being merged into the Specialist Crime Directorate to be designated SCD10. Now designated as SC&O 10, it falls under the purview of Specialist Crime & Operations.
The concept of covert policing evolved from that of community policing, but as criminality advanced, covert policing was seen to be needed to combat this.
CID detectives usually do not wear a uniform, which stemmed from the foundation of the CID. Because detectives are often concerned with the evidence gathering stage of an investigation, they are assumed by many to be the officers required to survey suspects as they go around their daily routines, however, this is not the case. 
Specialist Surveillance Teams exist which deploy a number of covert tactics in order to gather intelligence and evidence of subjects.
History.
Much of Britain's police service throughout the early to mid 20th century consisted of police officers walking a beat, one in each neighbourhood. This gave rise to the term "bobbies on the beat" and "golden age policing", as the officers walked constantly instead of patrolling the streets from police cars. Possibly the most accurate television portrayal of the archetypal British policing was the BBC programme "Dixon of Dock Green" (1955 to 1976).
The Criminal Intelligence Branch (which Covert Policing was a branch of before SO designations were devised) was formed in March 1960 and provided surveillance on known criminals, keeping pace with criminal methodology and technology.
2009 G-20 protests.
A Select Committee report on the 2009 G-20 London summit protests revealed that 25 undercover officers were deployed and were mixing with demonstrators. The overall charge, Bob Broadhurst, claimed that the deployment of undercover officers was unknown to him at the time, and that the plainclothes officers were "evidence gatherers".
Disclosure of relationships and children by undercover officers.
Around the end of 2010 and during 2011, it was disclosed in UK media, that a number of undercover police officers had, as part of their 'false persona', entered into intimate relationships with members of targeted groups and in some cases proposed marriage or fathered children with protesters who were unaware their partner was a police officer in a role as part of their official duties. Various legal actions followed, including eight women who took action against the Metropolitan Police and the Association of Chief Police Officers (ACPO), stating they were deceived into long-term intimate relationships by five officers, including Mark Kennedy, the first officer identified in 2010 as infiltrating social and environmental justice campaigns, and Mark Kennedy himself who claimed in turn that he had been incompetently handled by his superiors and denied psychological counselling. According to "The Guardian", Kennedy sued the police for ruining his life and failing to "protect" him from falling in love with one of the environmental activists whose movement he infiltrated.
It later emerged that Kennedy had previously undertaken criminal acts as part of his role for other countries, including Denmark where he stated that, in the guise of an environmental activist, he was used by the police forces of 22 countries and was responsible for the closing down of the Youth House community centre in Copenhagen, and in Germany, for German police, including arson. The use of undercover officers also caused the collapse of trials and led to the revelation of unlawful withholding of evidence by the Crown Prosecution Service. Six activists accused of conspiracy to commit aggravated trespass at Ratcliffe-on-Soar Power Station collapsed following the revelation of undercover police involvement, in which the police were described as having been not just observers, but agent provocateurs, and the Crown Prosecution Service (CPS) was forced to withdraw the case against the activists after Kennedy confessed to the set-up, evidence of which the CPS had withheld from the defence, along with secret tapes "that could have exonerated six activists, known as the "deniers" because they claimed not to have agreed to join the protest". CPS lawyer Ian Cunningham faced dismissal after a report by Sir Christopher Rose criticised him for his lack of candour.
In November 2015 the Metropolitan Police force apologized unreservedly to seven women "tricked into relationships" over a period of 25 years by officers in the Special Demonstration Squad (SDS) and the National Public Order Intelligence Unit (NPOIU). The officers involved had eventually "vanished", leaving questions and deceit behind, described by victims as "psychological torture". Financial settlements estimated at £3 million for the seven claimants were also made as part of the settlement.
Crown Prosecutors declined to bring charges against any police officers or their supervisors, including charges for rape and other sexual crimes (covering sex under false pretences, unconsented sexual acts, and other potential offences). The CPS statement stated that misrepresenting identity, and obtaining sexual consent due to a false identity, did not generally create an offence of rape in English law, other than in specific statuory-defined situations, and therefore rape charges would be unlikely to succeed. For similar reasons, indecent assault, procurement for sexual intercourse by false pretences, and misconduct in office were also felt to lack sufficient basis for a conviction.
The disclosures also led to the closing of the units concerned, and a public inquiry titled the "Undercover Policing Inquiry", concerning the conduct of police in undercover operations. The inquiry is led by senior judge Lord Justice Pitchford, a Lord Justice of Appeal and member of the Privy Council.
Media.
Several now-exposed undercover police are profiled in the book "Undercover: The True Story of Britain's Secret Police" (2013).
The play "Any Means Necessary" is based on the infiltration of the Ratcliffe-on-Soar power station protest. It was the staged at Nottingham Playhouse in February 2016.
A planned television drama series is based on the story of the undercover officers.
The police detective drama series Hinterland - Y Gwyll was broadcast from 2013 to 2016. Set in Wales, it was shot in English and Welsh. The series is a Fiction Factory co-production with S4C, Tinopolis and All3Media International for S4C, BBC Wales, BBC 4 and Netflix.