Three thieves ambushed the Chubb security guard and his colleagues as they made an early-morning cash drop to a hotel on Sussex St on June 7 last year.

MURDERS don't come much more cold-blooded than the slaying of Gary Allibon.

Three thieves ambushed the Chubb security guard and his colleagues as they made an early-morning cash drop to a hotel on Sussex St on June 7 last year.

Mr Allibon, who had already been the victim of one armed robbery, handed over the cash, turned away from his attackers and walked towards the hotel.

That should have been the end of it.

But inexplicably one of the thieves shot the 59-year-old guard in the back. He then walked over to the critically injured man, stole his pistol and left him for dead.

Yesterday Mr Allibon's widow Monica returned to the scene of the crime to urge witnesses to come forward.

She was there as officers from Strike Force Lorimer released new surveillance footage of the gang's stolen silver Audi S8 and the robbery.

The footage shows the car travelling north across the Harbour Bridge before having a minor accident while making a U-turn in pursuit of the armoured van.

"It's the most cold, ugly thing to do to anybody," an emotional Mrs Allibon said.

"It was cold-blooded murder."

But recent arrests over other unrelated high-profile murder cases have given her hope for a breakthrough.

"I've never given up," she said.

Nevertheless, the pain endures.

"Eleven months later, every day is still confronting. We were very close and very much together," Mrs Allibon said.