A British historian claims to have discovered a former member of a Nazi battalion that was involved in numerous World War II atrocities, living out his days in Lancashire, England.

“These people ought to be held accountable for what they have done, even if it happened many years ago,” Dr. Stephen Ankier told the Daily Mail.

Ankier said he had found military rosters, payroll lists and other documents from Poland and Germany that prove 88-year-old British citizen Mychajlo Ostapenko was a rifleman in Ukraine’s 31st Punitive Battalion, a unit of volunteers led by SS officers, and was held captive in a POW camp in Rimini, Italy, after being captured by British forces.

Ostapenko, who came to Britain in 1947 and was granted citizenship in 1956, denied the allegations, saying he was in Poland during the war.

“I don’t know nothing about what was going on,” he told the Daily Mail. “I was in hospital in Poland for about nine months with appendicitis. Then I was at home. I was in an army but I never fought anyone. I haven’t done anything wrong. I haven’t killed anybody. I was in the Rimini camp. The British looked after us well. I can’t remember anything else. I’m sorry.”

Ostapenko’s naturalization certificate listed him as a miner from the town of Accrington. He married a British woman and had two children.

However, if Ankier’s findings are correct Ostapenko could also have been a witness or even perpetrated heinous war crimes. The 31st Punitive Battalion was sometimes called Ukrainian Self-Defense Legion and became part of the 14th SS-Volunteer Division “Galician.”

It was involved in putting down the Warsaw Uprising, in which an estimated 200,000 civilians and rebel fighters were killed, as well as the destruction of Huta Pieniacka, a village in Poland that also served as a shelter for Jews, in which 1,000 people were killed.

However, when the unit surrendered itself to the British at the end of the war, calling itself the First Division of the Ukrainian National Army, its members presented themselves as nationalists dedicated to the anti-Soviet cause and were allowed to settle in Britain with minimal checks for war crimes.

While there is no evidence that Ostapenko took part in any war crimes, former Labour MP Andrew Dismore called on him to cooperate with police.

“Even if people like Ostapenko were not directly involved in war crimes, they may have a great deal of first-hand knowledge,” he told the Daily Mail. “If they have a clear conscience, there is no reason why they should not co-operate.”

Ankier previously made international headlines in 2013 after he discovered one of the unit’s commanders, Michael Karkoc, living in Minnesota. German authorities are now considering if there is enough hard evidence to prosecute Karkoc and have him extradited from the United States.

He also discovered that recently deceased British citizen Serhij Woronyj had been part of the same unit as Ostapenko.

JTA contributed to this report.