Scotland Yard's War Crimes Team, which is part of its Counter-Terrorism Command, has launched an investigation into the role of British mercenaries in fighting the Liberation Tigers of Tamil Eelam (LTTE) rebels in Sri Lanka during the 1980s.
The Metropolitan Police said it has received a referral in March concerning alleged war crimes leading to a scoping exercise, which has now been expanded into an investigation.
It follows revelations that a private security company, Keenie Meenie Services (KMS), trained an elite unit of the Sri Lankan police called the Special Task Force (STF) in the 1980s to fight the LTTE rebels.
The references emerged in a book by United Kingdom-based investigative journalist Phil Miller earlier this year, based on declassified UK government documents and freedom of information requests.
The book, Keenie Meenie: The British Mercenaries Who Got Away With War Crimes, had also claimed that the Indian Peace Keeping Force (IPKF) received air support from some of these for-hire UK pilots.
'We can confirm that the Met's War Crimes Team -- part of its Counter Terrorism Command -- received a referral in March concerning war crimes alleged to have been committed by British Mercenaries in Sri Lanka during the 1980s,' a Met Police statement said.
'Following receipt of the referral, the War Crimes Team began a scoping exercise into the matter and have subsequently launched an investigation.
'We are not prepared to discuss any further details of what remains an active and ongoing police investigation into this matter,' it said.
Keenie Meenie, from the title of the book, is thought to be an Arabic slang for covert activities and was run by a retired colonel, Jim Johnson -- a former Special Air Services (SAS) commander, who had conducted secret missions in Yemen and Oman.
Johnson's counter-insurgency experience came to the attention of then Sri Lankan President Junius Jayewardene at the start of Sri Lanka's civil war in 1983, when the Anglophile leader was looking for British aid to defeat the Tamil Tigers.
Britain refused to officially send troops to help Jayewardene, fearing it would have jeopardised 'substantial commercial and defence' deals.
"I welcome this police investigation which is long overdue. Much of the evidence against KMS is contained in British Foreign Office files which were kept classified for 30 years, allowing some senior KMS figures to pass away without ever facing justice," said Miller, in reference to the Met Police probe.
"More evidence is coming to light that shows KMS were linked to atrocities not just against Sri Lanka's Tamil minority but also against the Sinhalese majority, so there are lots of questions to be asked about the extent of this British company's role in Sri Lanka's turbulent history," he said.
The Tamil Information Centre (TIC) in London had sent a detailed dossier of evidence to the Met Police earlier this year.
"War crimes committed by the Sri Lankan state, ably assisted by British mercenaries caused death, displacement and massive suffering to the Tamil people.
"All of those who committed those war crimes should be brought to justice. We hope that this investigation is the first step to ultimately a successful prosecution," said Anuraj Sinna, a director of the Tamil Information Centre.
The KMS personnel are alleged to have flown helicopter gunships that were involved in attacks on Tamil civilians.
The company's staff also trained Sri Lankan paramilitaries and commandos as well as giving operational advice at the highest level.
Paul Heron, a solicitor at the Public Interest Law Centre which is representing TIC, said: "This is the first investigation that we know of into British mercenaries operating overseas and alleged to have committed war crimes.
"The KMS was involved in covert activities across the planet, from Nicaragua to Sri Lanka."
The KMS came into being in the 1970s with battle-hardened British veterans and, according to Miller's book based on previously classified accounts, were active in controversial operations around the world with the UK governments of the time unable to fully control them.
The IPKF is believed to have received air support from these for-hire British pilots, despite Indian diplomats publicly condemning the presence of UK mercenaries in Sri Lanka.
According to the book, India's secret use of British mercenaries lasted for four months after the Indo-Lanka accord was signed between former Prime Minister Rajiv Gandhi and Jayewardene in 1987.
The book also traces the involvement of British mercenaries in atrocities against Tamil civilians that occurred prior to the arrival of the IPKF.
The LTTE ran a military campaign for a separate Tamil homeland in the northern and eastern provinces of the island nation for nearly 30 years before its collapse in 2009 after the Sri Lankan Army killed its supreme leader Velupillai Prabhakaran.
Sri Lanka's human rights record, particularly over the impunity enjoyed by law enforcement officers, has been the subject of international condemnation.
The UN Human Rights Council has called for an international probe into the alleged war crimes during the military conflict with the LTTE.
According to the government figures, around 20,000 people are missing due to various conflicts including the 30-year-long separatist war with Lankan Tamils in the north and east which claimed at least 100,000 lives.