A Brighton man has been jailed for five years for his part in a failed plot to steal £200 million of diamonds from the Millennium Dome.

Kevin Meredith, 34, of Aucklands Drive, was found guilty of conspiracy to steal by an Old Bailey jury.

But boat skipper Meredith was cleared of plotting to rob the Dome in Greenwich, London. He had denied both charges.

Four other men were jailed for between 15 and 18 years for conspiring to rob the Dome's diamond exhibition. Had it succeeded, it would have been the world's biggest ever gems heist.

The jury of seven women and five men reached majority verdicts against the defendants after deliberating for nearly seven court days.

They found Aldo Ciarrocchi, 32, of Bermondsey, south-east London; Raymond Betson, 40, of Chatham, Kent; William Cockram, 49, from Catford, south-east London; and Robert Adams, 57, of no fixed address, guilty of conspiracy to rob.

Betson and Cockram were jailed for 18 years each. Adams and Ciarrocchi got 15 years.

The four had denied conspiracy to rob but admitted the lesser charge of conspiracy to steal.

As Judge Michael Coombe passed sentence, only Meredith appeared to show any emotion.

Sobbing could be heard from the public gallery as the judge told him he would spend five years in prison.

The judge said: "The fact is this was a wicked plan and one which was carried out to the minutest detail."

Referring to Meredith's defence, he said: "In my years at the Bar and bench I have never heard a defence of duress with less merit or substance."

The prosecution alleged that the gang intended to snatch the stones by smashing their way into the Dome on an earthmover, then escape across the Thames by speedboat.

They ram-raided their way into the Thames-side tourist attraction on a JCB but were caught red-handed by armed police.

They had been inches away from seizing jewels from the De Beers diamond exhibition.

The Millennium Star and the eleven Millennium Blue Diamonds - ranked among the finest in the world - had attracted thousands of visitors to the exhibition.

But unknown to the robbers the real jewels had been swapped with fakes after a police tip-off. The raid was foiled by the Flying Squad, backed up by armed officers.

Martin Heslop QC, prosecuting, said: "It was a remarkable police operation. But for their intervention they would have got away with £200 million worth of diamonds."

The gang had caused terror as they sped towards the vault in the JCB on November 7 2000.

A boat, skippered by Meredith, was waiting to take them across the Thames to a getaway van parked on the other side. But they ran straight into a police ambush.

Meredith was recruited at the last minute after a gang member dropped out.

He said Cockram coerced him into taking the speedboat across the river.

He owed Cockram - a casual acquaintance - money, and when he was unable to pay, Cockram told him to drive the boat and threatened his wife and family, he said.

His only act of dishonesty in his life was to watch TV without a licence, he told the court.

He was running his own charter boat, Random Harvest, from Brighton Marina when he met Cockram.