You could not have a more conspiratorial group

Martin Heslop QC Prosecutor

But Mr Cockran was himself filmed at the Dome with his alleged co-conspirator Raymond Betson by an undercover police officer, the court heard.

Police foiled the planned raid after mounting a sophisticated surveillance operation involving undercover officers and CCTV cameras, Mr Heslop earlier told the court.

In the dock are Kevin Meredith, 34, from Brighton, East Sussex; Wayne Taylor, 35, of Tonbridge, Kent; Mr Ciarrocchi, 31, from Bermondsey, and Mr Cockran, 48, of Catford, both south-east London; Robert Adams, 57, and Mr Betson, 39, of no fixed address.

They all deny conspiracy to rob.

Mr Heslop said 1 September was a significant day. Mr Betson had gone to the Dome at around 9am and Mr Cockran arrived 50 minutes later.

Video camera

"He was with a lady and child. You may think it was some form of cover," he said.

Mr Cockran, who had a video camera, then went into the vault and started to film, the prosecution alleged.

They later went to Surrey Quays before returning to the Dome again.

The men are accused of trying to steal diamonds worth �200m

A secret surveillance video showed them meeting a third alleged member of the gang, Aldo Ciarrocchi, at Surrey Quays, the court was told.

"You could not have a more conspiratorial group," Mr Heslop said of the video shot.

Other secretly filmed views of alleged Dome raiders planning the "robbery of the millennium" were shown to the jury during the second day of the prosecution's opening speech.

A stolen JCB earthmover - used to smash its way into the Dome in the attempt to snatch �200 million worth of diamonds - was videoed by police as the gang made dry runs during preparations months before, the court heard.

Charges denied

A white van which allegedly set out with the JCB on the day of the planned raid was also shown in black and white shots played to the jury on a giant screen set high above them.

They were playing for very high stakes - this was no ordinary robbery

Mr Heslop

Mr Heslop has alleged the gang's target "was nothing less than the 12 extremely rare and valuable diamonds" on display in a vault at the Dome.

He said the Millennium Star and the Millennium Blue Diamonds "may very well be the rarest and finest diamonds in the world".

Mr Heslop added: "They were playing for very high stakes. This was no ordinary robbery.

"The value of the diamonds is conservatively estimated, and I will pause here, at �200 million.

'Professional planning'

"Had they succeeded, it would have ranked as the biggest robbery in the world in terms of value.

"It could properly be described as the robbery of the millennium.

"It was planned professionally and carefully down to the last detail.

"The conspiracy was so well organised it almost succeeded. They smashed their way into the Dome at about 0930."

The trial was adjourned until Monday.