The thieves who took a Leonardo da Vinci painting worth an estimated £40m from a Scottish castle will probably make a ransom demand, an expert on stolen art said yesterday. The two men stole the painting, Madonna with the Yarnwinder, from Drumlanrig Castle, Dumfries and Galloway, on Wednesday, and fled with two accomplices in a car.Mr Ellis, who led the team that recovered Edvard Munch's The Scream three months after it was stolen in Oslo in 1994, said the theft of the Madonna had been professional. Pictures released yesterday from the castle's security system showed that the two thieves wore hats, dipped their heads and covered their faces as they passed the surveillance camera.The thieves overpowered a female guide and later abandoned their getaway car. The firm that insured the painting has offered a undisclosed six-figure sum for its return. Mr Ellis, the managing director of Trace, a magazine that helps to recover stolen art, believes the people behind the theft will probably try to claim a ransom or "reward" for the Leonardo's safe return. He said: "My feeling is that it will go quiet for a bit then there will be feelers put out to establish whether it could be ransomed back to the owners or insurers."It is at this stage the police will try to catch the thieves It is likely to be a cat-and-mouse situation for some time. The way the men bypassed the security system, went straight for the most valuable painting, and had a successful getaway all suggests it was a professional job."He said that the thieves may be preparing to trade the painting with other professional criminals "They will only get from 5 to 10 per cent of the value.

In the past, stolen art has been used as collateral for loans in setting up a bank for money laundering, and for exchange of drugs. But unless you are already in the international crime league you can forget it."The images released yesterday include an e-fit of a man who bought the thieves' getaway car, a Volkswagen Golf GTi, from the registered owner about two weeks ago.. When the police raided the pet food factory they found chicken carcasses rotting in the mud in the semi-derelict former knackers yard. One area was flooded with stinking water which had seeped from a septic tank, and rotten meat spilt from overflowing skips Rats were everywhere. Rats were everywhere. The Derbyshire plant was the centre of a hugely lucrative scam in which diseased meat was recycled and moved in maggot-infested vans to the shelves of some of Britain's best-known supermarkets.At Nottingham Crown Court yesterday three men were cleared of conspiracy to defraud. But six men have been convicted after more than five years of easily evading controls supposed to ensure the safety of food. Four of them worked for Denby Poultry Products, the "pet food" plant, and two were from a meat processor in Northampton, MK Poultry, which received much of the meat.Peter Roberts, 68, known as "Maggot Pete", ran Denby Poultry for six years and was found guilty of conspiracy to defraud on Wednesday, but had fled before the start of his trial.

He may be in Spain, where he owns property, spending some of the estimated £500,000 he made from the scam. Five other men had already pleaded guilty.About 450 tons of meat was trimmed and repackaged and shovelled into the human food chain via food brokers, convenience food makers and restaurants. Police estimate that the gang made profits of many millions of pounds after picking up the condemned waste, sometimes free, and selling it for up to £15 a kg. In little more than a year, they processed more than a million chicken and turkey carcasses.Before the plant was raided in March 2001, condemned meat had been sent to at least one school in London, Tesco and Sainsbury, Bupa care homes and even to the catering firm that served food at the headquarters of Derbyshire Police. Experts believe the meat could have proved fatal to the old and vulnerable.The meat was found to be contaminated with E.coli and bacterial hepatitis, but Meat Hygiene Service inspectors failed to spot that the "high-risk" chicken carcasses were being whisked away from slaughterhouses.When the plot was uncovered, more than 30 products were recalled in April 2001 at a cost of more than £1m, including chicken nuggets and jars of Shippam's pastes. Whether anyone had been made ill was unclear.After the case, police criticised the Food Standards Agency (FSA). Detective Inspector Neil Perry, who led the inquiry, said: "We don't believe that the FSA has taken this matter seriously enough.

There have been problems in convincing them about the risks posed to the public."The Department for the Environment, Food and Rural Affairs and Derbyshire County Council were responsible for regulating the Denby plant Both agencies denied they were to blame. A Defra spokeswoman said: "We were inspecting the plant as a pet food supplier, we weren't inspecting it as a human food supplier. It's the people who are buying it as bona fide human meat who should check it out."Derbyshire County Council, whose trading standards officers visited the plant twice, in 1999 and December 2000, said it "didn't uncover any significant problems".Since September 2001, all high-risk animal waste, including whole birds, has been stained with black dye, to try to prevent the trade in potentially diseased meat.The scam was rumbled only because of an anonymous tip-off to Amber Valley District Council. Yesterday Sue Sonnex, director of environmental services at Amber Valley, said: "This was an extremely small business with a small number of people able to exploit some real loopholes in the food supply chain to become very rich themselves. I'm uncertain that we have got an appropriate level of control."A waste food task force reported in January that a series of scandals had "undermined public confidence in food".