Sri Lankan President Mahinda Rajapaksa's scheduled speech on Wednesday at the Commonwealth Economic Forum was cancelled, amid concerns about possible demonstrations by Tamil groups protesting against human rights violations in his country.
Rajapaksa is also scheduled to attend a lunch for Queen Elizabeth hosted by Commonwealth Secretary General Kamalesh Sharma at Marlborough House.
The Commonwealth Business Council said on its website: "After careful consideration, the morning sessions of the Forum... have been cancelled and will not take place."
A spokesman for Scotland Yard said it had agreed to guarantee the President's security but the CBC had "decided it was not in their interest to stage the event" because of the extent of the policing required and the likely disruption to the city of London.
The Guardian reported on Wednesday that a Sri Lankan man, who was left scarred and suicidal after two weeks of torture, accused the British government of forcibly deporting asylum seekers who are then tortured in the island nation.
The victim reportedly told The Guardian that he was tortured over 17 days after being deported from the United Kingdom last year.
His torturers accused him of passing on to British officials information about previous beatings at the hands of state officials and other human rights abuses to ruin diplomatic relations between the two countries, the daily said.
Last week, the high court halted the deportation of 40 people to Sri Lanka at the last minute, citing human rights concerns, the daily reported.