He acted on very slight suspicion initially and then an intelligent appreciation of the situation Detective Chief Inspector Charles Naame

Police said they believe the five arrested men - four Indians and a Pakistani - are illegal immigrants and praised the action of the farmer, who has not been named for fear of reprisals.

The landowner had been asked by police to watch the wartime airfield as detectives had been tipped off it could be used for a smuggling operation.

He confronted a driver and passenger parked in a Land Rover by the airstrip at 0841 GMT.

Minutes later a four-seater Piper Cherokee landed on the runway.

Bribe refused

"The pilot spotted me - I assume he realised I was not one of his people and I saw he was going to take off.

"I drove my truck alongside in chase. The pilot had gone about 200 yards (183 m) and had just got up speed - I turned my wheel across and rammed him," he said.

The masked pilot ran off after the farmer refused a bribe of �1,000 to allow the plane to take off.

Detective Chief Inspector Charles Naam told the BBC he thought this was the work of a well-organised gang but said his team had a definite line of inquiry thanks to the farmer.

"He acted on very slight suspicion initially and then an intelligent appreciation of the situation," he said.

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