OFFICERS knew the evidence needed to convict Brown was like gathering pieces of a jigsaw puzzle – one missing piece could see the case fall flat and the offender walk free.

OFFICERS knew the evidence needed to convict Brown was like gathering pieces of a jigsaw puzzle - one missing piece could see the case fall flat and the offender walk free.

Armed with forensic evidence to back their CCTV footage, officers scoured Exmouth looking for proof Brown was the offender.

DS Hall said: "There was a plastic bag left by the offender so that was submitted for forensic analysis.

"Once we had an idea of a route, we used a tactical aid group to search the route we believed he had taken."

Gardens, roofs, drains and bins were among the areas searched by the specialist officers.

Coins, believed to have been dropped by Brown on his way home, were found in Exeter Road directly after the hold-up.

The key witness - the cashier - was questioned by specialist cognitive-trained interview officers.

Their specialist training enabled her to remember the offender's accent, the tone of his voice - even the colour of his eyes.

But a breakthrough for Exmouth CID came when tactical aid officers discovered an abandoned balaclava in a disused doorway in Exeter Road.

It was immediately submitted for forensic analysis - with officers driving the item to Forensic Science Service at Chepstow to harvest any DNA.

DS Hall said: "I wasn't away from my mobile phone at all. Even if I wasn't on duty, I was making calls to see if we had a result.

"I had a call one morning saying 'we have a result, we have a name for you'. It was a name that wasn't local [Brown had moved to Exmouth four weeks before the crime was committed].

"My opinion was, after doing some research, he fitted our profile.