Barnes Flying Squad is hunting a man believed to be a leading member of a gang which carried out a series of violent robberies targeting cash-in-transit vehicles throughout London, Surrey, Hertfordshire, Sussex and Merseyside.

Ian Dixon, 39, who lived in south-west London last year, allegedly played a leading role in a number of the robberies where firearms have been used to enforce threats, including an offence in 2007 where a custodian was stabbed in the thigh.

He has a distinctive tattoo on his right arm, which depicts a gun. He was featured on the BBC's Crimewatch programme in March this year but still remains at large.

Police say Dixon has access to firearms and is considered to be extremely dangerous. He should not be approached by the public.

As well as south-west London, he also has links to Liverpool, where he grew up.

Group for Securicor (G4S) is offering a reward of up to £25,000 for information leading to Dixon's arrest.

Two other men have been charged in connection with the robberies. Unemployed Nicholas Wordsworth, 34, and John Carvey, 39, both from Islington, were charged with one count of robbery of £13,000 from a Securicor custodian on March 8 in Lower Holloway, north London, and possession of a loaded semi-automatic pump action shotgun used during that robbery.

The incidents he was allegedly involved in spanned from June 2006 to March this year, with 17 of them being armed robberies.

Knives and firearms, including a loaded pump action shotgun, were regularly used to intimidate cash in transit custodians, with weapons held to the head, throat or torso of victims. In several attacks weapons were used and discharged.

One custodian was stabbed during one raid, while two others had firearms discharged towards them during another.

On another occasion shots were fired in the air, in order to escape from witnesses, who gave chase.

Anyone with information about Ian Dixon or his whereabouts should phone Barnes Flying Squad on 020 8247 7932 or Crimestoppers anonymously on 0800 555 111.