James and Wayne Snell planned a brilliant bank robbery after carefully surveying their target with their two accomplices.

They struck late at night, dressed in dark, anonymous clothing and wearing balaclavas. They made off with more than £100,000. It was the perfect crime, but for one tiny detail.

The car in which the four carried out their surveillance operation had a personalised number plate.

The licence plate of James Snell’s blue BMW read: “J4 MES”. It proved extremely memorable to passers-by outside a branch of the Halifax in Cardiff. It proved extremely useful to the police in tracing the culprits.

They traced Snell’s car to a flat in a suburb north of Cardiff, which in turn led them to a flat in another part of the city where the two brothers were caught red-handed, and somewhat red-faced, with £30,000 in bank notes.

James, 26, and his older brother Wayne, 34, were one half of a gang that also included Carl Campion, 44, from Birmingham, and Adam Abbot, 38, from Hyde in Manchester.

Judge Gareth Jones, at Cardiff Crown Court, described the raid in an affluent district of the town as a “professional, sophisticated, planned robbery on commercial premises”.

The afternoon before the raid, the four drove to the bank on one of the main streets in the district of Roath. As well as observing the BMW, witnesses saw them steal a heavy, metal drain cover.

At 11.20pm that evening the gang returned in another car, driven by James Snell, and ambushed two Group 4 Securicor workers refilling the cash machine. Two used the drain cover to smash through the glass while a third, armed with a bat, shouted threats. They drove away with £104,910 in £10 and £20 notes.

The empty cash boxes were dumped in woods. This piece of caution was undermined, however, because the drain cover, combined with the distinctive number plate, was tantamount to leaving a calling card at the scene. Prosecutor Tim Evans told the court:“It is clear their arrogance contributed to their undoing.”

The Snell brothers admitted robbery along with Abbot. Campion denied robbery but was found guilty and was jailed for 12 years. Wayne Snell was jailed for eight years. Abbot and James Snell will be sentenced at a later date.

Despite the convictions, £70,000 of the cash is still missing.

After the case, Detective Inspector Paul Andrews, of South Wales Police, said: “I would like to thank people who contacted us with information including the details of the car numberplate.”

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