The gang's plan failed when a motorist who was late for work removed the keys from the ignition of the unattended Christmas tree lorry.

They were seconds from taking the money when an unexpected police car appeared; the gang shot at the approaching vehicle and again made their escape in an inflatable speedboat.

This unsuccessful attack provided the police with important clues and led them to track some of the vehicles used in the raid to two isolated farms in rural Kent; these properties were then put under 24-hour surveillance.

The precautions taken by the Flying Squad included replacing the priceless gems with replicas of the same size (one of which is now in the Crime Museum[5]), allowing the originals to be stored elsewhere, as well as installing a false wall inside the exhibit room, behind which 20 police were waiting in full tactical gear.

[3] The Metropolitan Police identified the possible days the raid could occur and communicated this information to De Beers and the Dome's management.

The second aborted attempt occurred one day before the date of the actual raid but was cancelled upon the gang discovering the tide was too low to ensure a safe getaway.

Upon closer investigation, the detectives discovered that the tide was at its highest possible level each day when the robbery was aborted.

A further sixty armed Flying Squad officers were stationed around the Thames and twenty on the river to prevent escape attempts.

Before the raid, some officers were positioned behind a dummy wall, and others were dressed as cleaners and Dome employees, with their firearms concealed.

Before the raid, four members of the gang had been identified in a JCB earth digger, and all were wearing body armour and gas masks.

The men were armed with smoke bombs, sledgehammers, and nail guns to be used to penetrate the security glass that was protecting the exhibit.

The digger was used by the gang to break through the perimeter fence and to crash through the side wall of the Dome to reach the Money Zone, where the De Beers diamonds were kept.

Once inside, Ciarrocchi started throwing smoke bombs, and Cockram attempted to break the glass where the diamonds were stored.

The court heard that Betson, Cockram, Ciarrocchi, and Adams were caught by undercover officers in the Dome when they burst inside by using a JCB digger.

On the first day of the defence case, Cockram discussed the lack of security inside the Dome: "I couldn't believe how simple it was. ...

He stated that had the plan succeeded, "It would have taken a very short time from hitting the main gate to getting back across the Thames – five minutes maximum".

Called as a prosecution witness, Waring "totally denied" that he was part of the plan or had offered to act criminally by providing information on security.

[8] The gang had invested tens of thousands planning the raid and stored the equipment needed at a disused commercial yard in Plumstead, southeast London, as well as two remote Kent farms, near Maidstone.

Terry Millman, who had died of cancer before the trial, used the name T. Diamond when he paid £3,700 in cash to purchase a getaway speedboat at a yard in the seaside town of Whitstable, Kent.

[citation needed] At the trial, Crown Prosecutor Martin Heslop, QC, said that "the raid was planned professionally, carefully and down to the last detail. ...

Heslop stated that to minimize the risk to the public, "Arrangements were made to keep children away from the danger area, but for obvious reasons, it was not practicable to alert all staff to the possibility of an attack.

"[9] After three months of the trial, the jury of seven women and five men reached a 10–2 majority verdict against the defendants after they had deliberated for nearly seven court days.

[9] Cockram, sentenced to 18 years for his part in the raid, was awarded legal aid to sue the Metropolitan Police Service in March 2003.

In March 2010, the London Evening Standard reported that the gem would be sold in a collection at Sotheby's Hong Kong the following month.

The officer in charge of Operation Magician, Detective Chief Superintendent Jon Shatford, arrived in Spain with a team of three others and an emergency warrant for Hurley's arrest.

He was dubbed the "boatman" by the police as he was seen taking photographs of the Dome from vessels on the Thames and was organising the speedboat to be used for the getaway.

Once Hurley had been photographed, and his identity confirmed, a High Court judge in London issued a red extradition warrant for his arrest.