BP chief executive Bob Dudley was poisoned by Russian security services to “oust” him and force him to leave by the back door, according to a former employee.
Mr Dudley was forced to flee Moscow after blood test results revealed he was slowly being poisoned.
At the time of the alleged poisoning in 2008, Mr Dudley was a senior executive in BP and was running a joint venture called TNK-BP.
Ilya Zaslavskiy, who worked for TNK-BP, claimed only the Russian intelligence agency had the ability to administer a poison slowly enough to harm the boss, but not to actually kill him.
He told the Daily Telegraph: “The whole idea was to oust Bob Dudley and about 150 Western managers.
“The harassment of Western staff took place on many levels. They followed people, they broke into their apartments. One was warned it wasn't safe to return to Russia.
“With Dudley and a few senior managers, they also started to open different court cases against them personally rather than just BP.
“That was the first hint to Dudley he should get out. But he wouldn't. He was stubborn. He thought he could run the company because he had the law on his side, so he stuck it out in Moscow.
"Finally they decided to send him a better message by poisoning his food. Obviously we could never prove who exactly poisoned him.
"I was aware of these claims but I had it confirmed in 2016 by a former colleague who was a close adviser to Dudley.