A SERIAL conman who has preyed on pensioners throughout the North of England may finally be snared after tricking a Darwen grandma out of £200.

But other pensioners were today advised to remain vigilant as the man remains at large, and warned never to buy goods from people who knock at the door.

Police have been tracking the conman for two years as he deceived a trail of vulnerable, elderly people across West Yorkshire and East Lancashire.

He offers two alarms, one for the house and the other portable, for £200 -- but they can be bought over the counter at Halfords for £10.

Police and Trading Standards have been unable to press charges as selling-on an item is not an offence. But when he called at 75-year-old Margaret Shorrock's home in Woodville Terrace, Darwen, he pretended to be working for Age Concern and Help the Aged on behalf of the police. Such a deception is a criminal offence.

Mrs Shorrock is furious.

She said the man told her he was conducting a survey into burglary concerns on behalf of Age Concern and Help The Aged.

Mrs Shorrock paid £199.98 in cash for the two alarms -- one to carry with her and the second to be fitted close to her front door.

But the man never returned to fit one alarm by the door the following week, as he promised.

Mrs Shorrock said: "When he didn't come back I realised that I had been done. He had talked a lot of sense and it seemed a right good idea to have the alarms. But they are obviously not what I thought they were."

Chris Allen, head of Trading Standards and advice services for Blackburn with Darwen Borough Council, who is looking into the matter, said: "The stock advice is don't buy anything from anyone who simply knocks at the door." Tony Vickery, sales and marketing manager of Cambridge-based Talkeasy Ltd, which manufactures the alarms, said: "This has been going on and off for two years. Police have had trouble in the past as he hasn't told his victims anything. Now if he is posing as an Age Concern or Help the Aged officer, that's a different matter. We are extremely concerned about this for obvious reasons. This man preys on vulnerable elderly people."

Vicky Shepherd, of Age Concern for Blackburn and Darwen, said: "We have definitely not had anyone in that area doing that."

Det Sgt Ian Critchley, of Darwen CID, confirmed they were looking into the possibility that the offender was the serial conman.

"I have heard of this man before," he said, "we are investigating the matter."

Anyone with information should call Darwen CID on 01254 353842, or Crimestoppers on 0800 555 111.