This was the moment when one of Britain's most prolific armed robbers staged his last security van hold-up.

Outside a HSBC bank in the Hampshire town of Chandlers Ford, Mark Nunes ran towards a G4S cash van, a Beretta 9mm pistol in his outstretched hand pointed directly at Michael Player, the guard.

"Gimme the f***ing money and open the van," Nunes, who was wearing a balaclava, shouted as he pushed the gun into Mr Player's face.

As Mr Player moved to put the cash box on the ground, Nunes struck him on the wrist with the pistol butt. The blow hit his metal watchstrap but still drew blood.

"All I could see was the gun, my eyes were fixed on it," Mr Player told The Times. "I was remembering my training - make no eye contact, put the box down."

At that instant a police sniper fired a single shot and Nunes fell backwards. He was dead.

Simultaneously a blue Volvo swung out of a disabled parking bay and braked by the van with its rear passenger door open.

This was the getaway car, intended for Nunes, 35, and his accomplice Andrew Markland, 36, who was now running across the road.

But instead of jumping into the car, Markland ran past and picked up the gun. Another police marksman fired and Markland fell, dropping the gun. As he lay on the ground there was a third rifle shot. His wounds were fatal.

Suddenly there were armed police everywhere – prodding the men on the ground to see if they were still armed, trying to talk to the shocked security guard and running for first aid equipment.

Because of the blood and the pain in his wrist, Mr Player thought he had been shot. "Most times, we don't come off better," he said.

In the confusion, the Volvo sped off. Its driver, Terry Wallace, was tracked as he dumped the car and made his way by train back to south London and the estate in Brixton where Nunes lived.

Wallace made contact with other members of the Nunes Gang which had carried out at least 18 cash van robberies over the previous 18 months. The Metropolitan Police's Flying Squad, which had been watching and gathering intelligence on Nunes for months, was not far behind. A surveillance camera hidden in a tree outside Nunes's flat filmed Wallace - gesticulating with his arms as he described the shooting.

Yesterday, at Kingston Crown Court, Wallace, 26, and three other members of Nunes's gang were convicted of conspiracy to rob. Three other men have already admitted offences linked to the parts they played as drivers, look-outs, scouts and robbers in his criminal organisation. All the men now face lengthy prison sentences.

Brendan Kelly, QC, for the prosecution, told the court: "Despite their skill, their planning and their patience - their luck ran out."

From the time he left prison in 2005 until the day he died, Nunes had been planning and executing robberies across southern England - from Ipswich and Cambridge to Bristol and Bath. They made off with at least £500,000.

Nunes did not take part in every raid, but had organised each one - recruiting the team and carrying out extensive reconnaissance. The indictment listed 18 raids but police believe the gang was as many as 10 others.

A career criminal, Nunes served three years and nine months of a jail term for a cash van raid in London in October 2000.

Immediately he was freed, Nunes took up where he left off but deliberately targeted deliveries outside the capital. His theory was that cash vans would be less security-conscious in the provinces and the Flying Squad would not be on his tail.

Nevertheless, he took enormous care to cover his tracks. The locations of the target banks were carefully chosen - quiet streets with good escape routes for robbers on foot and in cars.

Two or three vehicles would be stolen, or bought for a few hundred pounds, to be used in each job. A getaway car would be parked near the scene perhaps a day before the robbery and the gang would travel to the robbery location in two other cars which were then abandoned.

He frequently employed white drivers, like Wallace, believing that black men would attract too much attention in provincial towns.

Nunes also impressed on his men the need to use and frequently discard pay-as-you-go mobile phones which were difficult to trace.

The police had been on his trail for months before he was shot at Chandlers Ford. Phone analysts wrestled with the puzzle of constantly changing phone numbers to keep track of who Nunes was talking to, where they were going and what was being planned.

One detective said: "We knew they were at it, but Nunes took his job extremely seriously and he was almost impossible to pin down. We might have one of them under surveillance for a couple of weeks and as we're watching him doing nothing, a robbery takes place somewhere else."

In six of those robberies, the ones in which Nunes played a direct part, firearms were used. Security guards were punched, kicked, pistol-whipped and threatened. Sometimes the gang escaped empty-handed, often they got away with just one cash box holding £25,000 while their biggest haul was £165,000 from a van outside a Lloyds TSB branch in Bristol in May 2006.

Whether he was present at the robbery or not, Nunes took the largest share of the proceeds.

He lived in a council flat with his partner and family, but Nunes flashed his cash on a Yamaha R1 motorbike, drove a BMW M3 and had a rented bachelor pad equipped plasma TVs and games consoles.

Adrian Johnson, 28, one of Nunes's key lieutenants, had a plasma TV in every room in his flat, a Brocock converted pistol in his garage and a shoebox containing £8,000 cash by his bed. In his defence he claimed to be a cannabis dealer.

Most of Nunes's team came from Lambeth, South London, with several of his main accomplices being friends since childhood. June 2007 was the first time all the key members of the gang were out of prison at the same time and the point at which the robberies reached a pitch. On June 12, two raids were carried out - one in Cambridgeshire and one in Gloucester.

But the picture developing from mounting intelligence meant the net was closing. Nunes was under surveillance as he travelled to Chandlers Ford on a series of reconnaissance trips.

Flying Squad, surveillance and firearms teams were lying in wait for three days before the robbery attempt. But even to the last, Nunes almost outflanked them. Markland and Wallace were in sight of the police but they had lost Nunes until he appeared with the gun in his hand.

His death and that of Markland have been investigated by the Independent Police Complaints Commission, which is expected to publish its preliminary findings within days. An inquest will follow at which the families of the dead men will demand to know why they could not have been arrested instead of being shot.

One family member said: "Mark was not a killer, nor was Andrew. The police allege he was responsible for a lot of robberies, but do they say he was a killer? No.

"The police wanted to murder Mark because that was the only way they could get him."

Wallace, Johnson, Leroy Wilkinson, 29 and Victor Iniodu, 34, were convicted of conspiracy to rob after a five-week trial. Three other men - Leroy Hall, Leon McKenzie and Brian Henry - admitted the charge.

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