Michael Openshaw and Robert Barrett ignored the protests of the pictures' owner Dr Percy Thompson-Hancock as they took the two canvasses - 'Children on a Promenade' and 'Family of Three' - from his living room wall, leaving a �10,400 cash 'payment' behind.

They sent Dr Thompson-Hancock �6,000 in the post a few days later but it still came nowhere near the true values of paintings, the jury at Southwark Crown Court were told.

Lowry was born in Manchester in 1887

The distraught doctor and his family desperately tried to retrieve the paintings, unaware that they had been auctioned off by Bonhams for �78,000.

Eight months after the theft, the two appeared - with a price tag of �215,000 - at a Bond Street art gallery where they were spotted by Dr Thompson-Hancock's granddaughter.

'Despicable' act

Neither of the two men showed any reaction as the jury convicted them of two counts of theft. They rejected their claims that they had been victimised by the former doctor's "greedy" relatives after they had realised how much the oils were worth.

Passing sentence, Judge David Elfer QC told them: "What you men did was despicable. It was in fact a determined crusade by you to get from the doctor the best pieces that he had."

He said they had pestered their elderly victim repeatedly to part with the paintings, until finally they decided to take no more notice of his refusal to sell.

Lowry painted industrial landscapes

The court later heard that Mr Openshaw had only one previous conviction against him, but that Mr Barrett had a list of court appearances dating back 28 years.

They included stealing �9,000-worth of antique furniture from the home of a 90-year-old deaf and bed-ridden man.

Police believe the pair had spent years preying on elderly people across southern England.

Case officer Detective Constable Tim Snuggs said: "This case highlights the danger waiting for the old and frail, who should receive respect but don't, who cannot defend their homes and valuables and who don't know whom to trust."

He said it was difficult to gauge the extent of this sort of crime as victims were often too old and scared to come to court.

The five-day trial heard that Dr Hancock and his wife had built up a small collection of antiques and works of art including the two Lowrys over a number of years.

About five years ago, Robert Barrett and Michael Openshaw called round expressing an interest in some of the items.

They seemed "nice and sociable and appeared genuine" the doctor recalled, and he sold them a number of his pieces.

However, he always made it clear that the paintings, which he intended to leave to his two daughters, were not for sale.

It now seems likely that the two oils will eventually be returned to Dr Thompson-Hancock and his wife.