The £350,000 boats could exceed 70mph (112km/h) and were virtually untraceable on radar. Many were painted grey or black to make them less visible in water.

Ipswich Crown Court was told that Neil Davison, 39, and Ellen George, 41, had altered the boats, known as ribs, to make space for up to six tonnes of drugs. The prosecution alleges they knew that their clients included smugglers who trafficked drugs between Africa and Spain. In an e-mail sent to a potential customer, Mr Davison boasted that his boats were “uncatchable” and had a “low radar signature”, the jury was told.

The couple were arrested in March 2004 in a joint operation by British and Spanish customs officers. Revenue & Customs had placed them under surveillance after Spanish authorities seized several boats. The couple’s business, Crompton Marine, also sold vessels to Spanish police.

When police searched the couple’s home in Lowestoft, Suffolk, they found £1.2 million in cash stuffed in holdalls and hidden in cupboards and under the stairs. A further €1 million (£657,000) and £39,000 in cash was found at a home where Mr Davison was staying in Málaga.

George admitted money-laundering and possession of criminal property at an earlier hearing and is awaiting sentence. Mr Davison remains on bail in Spain where he faces drug-smuggling charges.

Simon Draycott, QC, for the prosecution, said that one prototype boat made and fitted-out by Crompton Marine could travel at 50mph with a load of six tonnes and five people on board. “This was such a powerful boat, it could carry a lot of drugs, a lot of contraband and still go so fast it could outrun any maritime craft,” he said.

“The ribs were built, sold and transported to southern Spain, North Africa and Morocco.”

Details of the boats emerged yesterday at the trial of Ian Rush, who is accused of selling Crompton Marine boats to drug dealers after the arrest of Mr Davison and George.

Mr Draycott told the court: “Davison, George and Rush knew those buying the boats wanted them for one reason — to transport drugs and contraband from North Africa to southern Spain. They also knew that the money used to pay for the boats was coming from the proceeds of crime.”

Police allegedly found plans for a 108ft (33m) boat that was big enough to carry five smaller boats. It was never built.

The couple left a paper trail of forged documents at their home, Mr Draycott said. The papers included forged ownership and competency certificates, which were handed over with the boat to help to hide the buyer’s identity.

Mr Rush, 42, of Butterwich, Lincolnshire, denies a charge of conspiracy to obtain criminal property. Philip Hackett, QC, for the defence, described Crompton Marine as “a moneylaundering outfit” using a web of offshore accounts and fake invoices, but stated that, after the arrest of Mr Davison and George, Mr Rush ran the business entirely properly.

He said that Mr Davison and George had generated £2.7 million in assets and moved £16 million across borders between 1998 and 2004, and that it was unlikely that all of this money came from sales of boats. He said that Mr Rush had never built boats like those described by Mr Draycott.

The trial continues.

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Time-worn Freddie gives up Test matches
• Brighton company 'involved in cyber attack'
• The art of survival: it’s all in the mind