It was the moment an 18-month crime spree was brought to a dramatic end with brutal efficiency in just a few fatal seconds.

Dramatic footage of a police marksman shooting dead robbery mastermind Mark Nunes and his accomplice Andrew Markland was captured on camera by a police surveillance team.

They had been lying in wait for Nunes' prolific gang at Chandlers Ford, Hampshire - their next intended target in a string of raids on security vans delivering cash to banks across the south of England.

As Nunes struck, holding a pistol to the head of the guard, he was cut down by the marksman's bullet within seconds.

As he lay on the ground, Markland ran towards his stricken colleague and attempted to pick up the weapon. He too was gunned down almost immediately.

The footage, which has never been seen in public, was played to jurors at Kingston Crown Court where today they found four men guilty of being part of Nunes' gang.

Nunes had been described in court as ''meticulous, careful and hard-working'' and had enjoyed ''considerable success'' in his criminal enterprise.

Following his release from prison for similar robberies, Nunes was soon busy recruiting for his gang among criminal networks in south London. Despite being the boss, Nunes was not adverse to getting his hands dirty himself and often played the robber's role.

By the time he arrived in Chandlers Ford on a sunny morning on September 13 last year, his team had already hit 18 security vans in 18 months - his well-practised methods netting them £500,000.

But this time officers from the Metropolitan Police's Flying Squad, who had been tracking the gang, were ready and waiting.

A surveillance team were filming from a vantage point opposite the HSBC bank while police marksmen had taken up their positions. Other armed officers were poised in a nearby public toilet block.

As a Group 4 security van pulled up in a disabled parking space next to the bank, a guard got out of the back of the vehicle.

At this point Nunes is seen on film running towards him.

As he does so, a police officer observing the event is heard to say: ''Robbery, robbery, strike, strike, strike. He has a gun to his head.''

The next thing heard is a shot as Nunes slumps to the floor.

''One man down,'' an officer is heard saying into the radio.

Markland is then seen running into shot and attempts to pick up the weapon dropped by his accomplice.

He too is shot and falls to the ground. A third shot is then heard on the video.

Soon the area is filled with officers while getaway driver Terence Wallace speeds off in a blue Volvo, managing to escape.

He is later captured and, like the rest of Nunes' gang, eventually brought to justice.