Omar Mohammad, 26, a Trinidadian national from South London, was detained on Friday night as he planned to board an aircraft for Britain. Police found two vials of powder in his bag, according to reports. Scotland Yard detectives are aware of the arrest but have not sent an officer to interview Mr Mohammad. His arrest comes while Trinidad and Tobago security forces are investigating three bombings in the capital, Port-of-Spain. The authorities are on alert for a fourth bombing after FBI warnings.

A police officer said: “We have detained a man under our Prevention of Terrorism Act. We are trying to ascertain what he was in Trinidad for and what his modus operandi was.”

Police also raided the house of Mr Mohammad’s grandmother, Zalika Mohammad, 71, and took away a computer and other materials. She said that Mr Mohammad had been in Trinidad for three months and had nothing to do with Muslim extremists.

She said: “Around 11pm they came pounding on the door. I get up and saw my grandson with the police. He said ‘grandma, they open up my suitcase and take the ‘surma’ and Epsom salts’.” Surma is a cosmetic used as an eyeliner.

According to Mrs Mohammad, her grandson married a woman from the island two weeks ago and had been staying at a house belonging to a company for which his London-based father works.

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