Elderly and vulnerable people - and their friends and families - have been urged to be on their guard against fraudulent individuals who may look to prey on pensioners.

The warning has been issued by Detective Sergeant Dave Kirkham of Norfolk police's economic crime unit and comes as convicted art fraudster John Drewe was jailed for eight years.

Drewe, 64, was said to have carried out a 'systematic and wholesale' fraud on Jeanne Du Feu who has lived since 2005 at Cranwich, near Thetford.

Det Sgt Kirkham, who led the complex investigation, said: 'There's quite a lot of evidence out there that the offenders do target the elderly. Put yourself in the position of a conman - if you set out to con 20 or 30 somethings they are not at the age of life where they've got money to rob. They are all mortgaged to the hilt.

'You target people in their 70s and 80s and they're sitting on the nest egg that they've built up.

'There's a message there right across the board which should be to all people - if you know people who are getting a bit doddery keep an eye on whose talking to them.'

Det Sgt Kirkham said women seemed more susceptible to lottery type frauds - where they receive emails or phone calls to say they have won a foreign lottery, while men were more likely to be conned into investing money in share scheme type scams.

But he also warned that people from religious backgrounds needed to be particularly vigilant when it came to protecting themselves against unscrupulous people.

He said: 'Jeanne Du Feu was a practising Quaker who wanted to see the best in everyone and devout religious people do not always spot the devil at work.'

Drewe, who was described by Jude Alasdair Darroch as the 'most devious and dishonest' person he had ever dealt with was convicted last month following a lengthy trial at Norwich Crown Court of theft of the �240,000 proceeds from the sale of the victim's house in Charlton, south London.

He was also convicted of fraud involving the transfer of the title of the property where she lived in Norfolk, which was valued at about �425,000 which he got transferred to his company Energy Resources Group, which had never traded or had any assets.

The jury could not reach verdicts on four further fraud counts and these were ordered to lie on file.