Prince Adegbenie Olateru-Olagbegi hoped the pungent vegetables would provide the ideal cover for the illegal consignment as he arrived at London's Heathrow airport on a Virgin Atlantic flight from Lagos.

The 55-year-old prince, a member of a Nigerian royal family, packed his luggage with shrimps and other smelly dried fish in an attempt to throw customs officials off the scent. But he reckoned without the keen nose of a sniffer dog called Max that intercepted him in the nothing-to-declare channel.

A black holdall was found inside his suitcase containing 23 apparently ordinary onions and the fish, his trial was told. A closer inspection revealed 17 of the onions had been carefully cut open and packed with small carbon paper wraps. The wraps contained a total of 3.21kg of 67% pure cocaine.

The prince denied all knowledge of the drugs but was convicted of smuggling on September 1 this year following an eight-day trial at Middlesex Guildhall crown court in central London. He told his trial that one of his 149 siblings was king to 450 000 subjects in Owo, southern Nigeria. His late father was knighted by the Queen in 1960.

Sentencing him at Snaresbrook Crown Court, east London, on Tuesday, Judge Farouk Ahmed said Adegbenie had used his high status to be waived through Nigerian customs and it was unlikely he was a "hapless drugs mule".

South African police searching Nigerian drug dealers, who force-feed girls crack and heroin and then prostitute them so that they can pay for their drugs.