Scotland Yard has apologised and paid substantial compensation to a man who was fathered by an undercover police officer who formed a long-term relationship with his mother in the 1980s in order to spy on political campaigners. The Metropolitan police has been compelled to pay the confidential sum after the man said in a lawsuit that he suffered psychiatric damage after discovering, at the age of 26, that his father was not the committed leftwing protester he had been led to believe. He discovered his father, who abandoned him as a two-year-old child, was in fact Bob Lambert, a police spy who had deceived his mother into an intimate relationship as part of an operation to infiltrate animal rights and environmental groups. Lambert’s alter ego was that of a long-haired anarchist by the name of Bob Robinson. When his undercover stint drew to a close, he disappeared completely from the lives of his long-term girlfriend and child. Lambert has been one of the most controversial undercover officers sent to infiltrate political groups as part of a secretive, four-decade operation that has been unearthed by the Guardian over recent years. At least two other police spies are known to have fathered children with activists they met while undercover. The activities of the undercover officers – who adopted the identities of dead children to lend their cover stories credibility – are due to be examined in a much-delayed public inquiry, headed by retired judge, Sir John Mitting. The inquiry, which was announced in 2014 by Theresa May when she was home secretary, is due to start hearing evidence on 2 November. Now 35, Lambert’s son was given anonymity during his lawsuit, in which he was referred to as TBS. He only discovered his father’s real identity by chance, more than two decades after he was born. Lambert was unmasked in 2011 following investigations by the Guardian and campaigners he had infiltrated. In 2012, TBS and his mother, known only as Jacqui, found out Lambert’s real identity after she stumbled across a news article about him in a newspaper. Until that point, Lambert had not made any move to get in touch with either of them since he vanished from their lives in 1988. The Met has previously paid £425,000 to Jacqui, following her legal action. She had contemplated suicide and received psychiatric treatment after discovering how she had been deceived in a police operation to gain information on activists. The Met settled the lawsuits from TBS and his mother without disclosing any official documents that would shed further light on Lambert’s activities. TBS told the Guardian that there was “a sense that the Met were still trying to cover up as much as they can”. He added: “It feels as though as they are not genuinely wanting to put a wrong right. I don’t think they have ever really been that concerned about that. They were quite happy to leave all this in the past and not let anyone know the truth.” He said he had yearned to have a father figure when he was growing up and now felt that his birth and childhood had been based on a lie, causing him confusion and distress. TBS added that he said it was frustrating that the Met had failed to come forward many years ago to tell him that Lambert had been an undercover officer. “Someone senior who knew what had happened should have flagged this up to say this is going to cause a lot of hurt,” he said. His lawyer, Jules Carey of Bindmans, added that his client sent the Met a list of questions about the operation but the force “managed to sidestep them and concluded the case by paying him substantial damages and apologising”. Lambert’s undercover role began in 1984, when he was tasked with infiltrating leftwing groups, stealing the identity of a seven–year-old boy who had died of a congenital heart defect in 1959. Adopting the identities of dead children was a routine tactic at the time for Lambert’s covert unit, the Special Demonstration Squad (SDS), which spied on thousands of activists over its 40-year existence. In what is now known to have been a common practice among SDS officers spying on activists, Lambert also formed romantic relationships to gain credibility. One was with Jacqui, who at the time was a 22-year-old animal rights campaigner. Lambert was at her side during 14 hours of labour when she gave birth to TBS in 1985. According to Jacqui, he seemed besotted with their son. Lambert gave the impression of being a devoted father. He also lived with Jacqui and TBS until he was two. During his stint undercover, Lambert allegedly set fire to a branch of Debenhams as part of a campaign against the fur trade – but he denies the claim. However, in 1988, in an attempt to lend credibility to his imminent departure, Lambert told Jacqui and others that police were close to arresting him. He then claimed to have have fled to Spain. In reality, Lambert resumed working for Special Branch in London and took on a more senior role, running the SDS’s secret operations in the 1990s, which included monitoring the family campaign of the murdered teenager Stephen Lawrence. Peter Francis, one of the undercover officers managed by Lambert, said he had told him that he should always use contraception when sleeping with political campaigners. Francis later became a key whistleblower, helping expose the tactics used to gather intelligence on political activists. Throughout the period he was undercover, Lambert was married with two children – a fact concealed from Jacqui. Jacqui was left to raise their son on her own, and TBS grew up believing that his father was a political activist who had had no choice but to flee abroad to avoid jail. Helen Ball, a Met assistant commissioner, wrote to TBS on behalf of Cressida Dick, the Met commissioner. “I wish to express my unreserved apology for the Metropolitan police’s role in the circumstances that led to your father’s relationship, as an undercover officer, with your mother, which culminated, years later, in the realisation that what you had been led to believe about your father and your home life, and the reasons given by your father for leaving the family home were based on a fundamental deceit,” she said. “The fact that you did not know the truth of the situation for such a prolonged period can only have made that realisation all the more upsetting.”