Children as young as 13 raided £100,000 from security vans while being directed by modern-day Fagins

Ali Lwanga, 21, used a McDonald's restaurant as a recruiting ground.

His gang, dressed in school uniforms, robbed guards carrying boxes of cash from shops to Group 4 Securicor vehicles.

'Paid a pittance': Ali Lwanga was compared to Fagin from Oliver Twist, right

Lwanga paid them a paltry fee in return for handing him the loot, while he kept at a safe distance in case anything went wrong.

Today he was facing a lengthy jail term after being caught by a new weapon  -  a dye called SmartWater that exploded from the cashboxes and permanently stained the banknotes and the robbers' skin.

Four teenagers aged between 14 and 16 admitted conspiracy to rob at Wood Green Crown Court, in North London. The youngest was 13 at the time of the offence.

Lwanga protested his innocence but was found guilty by a jury of three counts of conspiracy to rob.

New weapon: How Ali Lwanga was caught

Outside court, police explained how Lwanga had turned a McDonald's in Canning Town, East London, into a 'recruiting headquarters'.

They likened him to the villain Fagin, in Charles Dickens's Oliver Twist, who ran a gang of child pickpockets.

Detective Chief Inspector Gary Donnison from the Met's Flying Squad said: 'Lwanga was a very dangerous, ruthless Fagin-type character, employing young men tocarry out the thefts on his behalf.

'He was looking to recruit young boys whom he paid a pittance for committing these crimes.

'They would go out, commit the crimes, take the money back to him and he would take the greatest share. They were wearing school uniform under their hoodies.'

Lwanga, of Baron Walk, Canning Town, would pay the juveniles less than £100 a time to steal the cash boxes from security vans.

The boys were not armed, but 'rushed' the guards and wrestled the boxes from them.

On January 18 this year, Flying Squad officers carrying out surveillance on Lwanga watched the group looking for a van to rob. They settled on a Loomis vehicle in Enfield, North London. Loomis is the cash-handling arm of Securitas.

Police said three of the youths, who cannot be named for legal reasons, were in a stolen Renault Megane, while Lwanga directed operations from a Vauxhall Astra. The fourth boy was in a car nearby.

Two of the youths overpowered a security guard, stealing a box containing £3,640. After officers watched the box explode in the back of the Megane, they arrested the boys.

Lwanga was tracked down and arrested three weeks later on February 12. Police say he orchestrated at least nine robberies in less than two months, netting more than £100,000.

Four of the robberies involved SmartWater dye, and some dyestained cash was found beneath a mattress at his aunt's house.

DC Laurie Bays said: 'This is the first time SmartWater evidence has been used during a trial to help us convict a cash-in-transit robber.'

Tim Ramm, of Group 4 Securicor, said the SmartWater was now put in every cash box. 'It has been a multi-million pound investment but we believe it will bring a lot of convictions,' he said.

All the defendants will be sentenced at Wood Green Crown Court after pre-sentence reports.