New evidence has emerged which could prove the innocence of a Scot facing life in a Kenyan jail for drug smuggling.

Jack Marrian, 31, the grandson of the 6th Earl of Cawdor, is to be tried next month after 200lb of cocaine was found hidden in a shipped consignment of sugar destined for his trading company in Kenya.

It was discovered by police in Mombasa in July, and it originated in Brazil, where agents from the US Drugs Enforcement Agency (DEA) suspect that criminals hid the drugs in a container without the knowledge of Mr Marrian or his company.

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Spanish, US and British anti-drugs trafficking agents tracked the container, which headed for Valencia before continuing to Africa.

Now a former DEA agent, Anthony Coulson, who was in Nairobi at the time of the drugs raid in Mombasa, has told the Mail on Sunday newspaper that agents have evidence that could exonerate Mr Marrian.

He said: "The US, British and Spanish authorities - the Guardia Civil - all have the information which exonerates Jack Marrian and his company from knowledge or involvement in the cocaine shipment.

"They have all made public the fact that an innocent man has been falsely accused of a crime.

"The Kenyan police and prosecutors are also fully aware but are pressing ahead with charges against him.

"They have the documents detailing how Jack Marrian and his company were unwittingly exploited by traffickers."

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It is alleged that representatives from the UK's National Crime Agency (NCA) had visited Mr Marrian in jail and told him of a classified report which contains the name of perpetrators, intelligence agents and records of phone calls related to the case.

It is unclear whether the Kenyan authorities have this report, although the NCA has said it has passed the report on.

Mr Marrian's home in Nairobi was raised on July 31.

He was kept in jail for weeks until his release on £500,000 bail.

Mr Marrian said he had never had dealings with police before, "not even a speeding ticket."

Mr Marrian said last week: "I've never been inside a prison before. I am innocent. There is no possibility of proving me guilty."

Mr Marrian's lawyer, Sheetal Kapila, said: "We are not seeking any favours.

"All accused persons are entitled to what we are asking for.

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"The constitution of Kenya provides that every accused person has the right to a fair trial, reasonable access to evidence."