Farmers have been given a harvest-time warning to protect their tractors and combines from thieves who are increasingly targeting high-value GPS systems.
Figures published this week by insurers NFU Mutual reveal that although the cost of rural thefts dropped by 20pc in the East last year, claims for satellite guidance systems had doubled across the country.
The report said demand across the globe was fuelling the thefts of the portable, high-value units which had become a target for organised crime gangs.
Norfolk police said there were some simple security tips that could prevent farms from suffering a costly loss of equipment which could delay their vital harvest operations.
Rural crime officer PC Chris Shelley said: "Where possible, you should remove the equipment from the tractor, and certainly avoid leaving tractors in the field at harvest time.
"I know that's difficult when you are working such long days, but don't leave it vulnerable.
"It is also important to use the built-in security measures they have started to put into the newer units, where they have a PIN lock code.
"Also, just marking it with a postcode and surname, even if it is just with a black marker or a simple engraving tool, is enough for us to work on if it gets stolen and recovered."
PC Shelley said satellite guidance units were likely to remain a target for thieves until they became less easy to remove from farm vehicles.
"The problem with GPS thefts is that they are like car stereos used to be - those thefts have been designed out now, and it is a crime you don't see any more because you don't see removable car stereos.
"Ultimately the GPS systems will be built into the dashboards, but for now you need to mark them to make them less easy to sell on the black market.
"They don't lose very much money on the second-hand market, so they are really easy wins for thieves and organised crime gangs."
PC Shelley said although GPS guidance systems were stolen from tractors at three Norfolk farms in two nights in April, there had not been a large number of similar thefts so far this year.
But he warned that could change if expensive machinery is left vulnerable during the busy harvest season.
CASE STUDY: Crime's impact on farming families
Thieves stole a global positioning system (GPS) from Jim Papworth's family's farming business the day before last summer's harvest was due to start.
The company's £450,000 Claas combine was parked up behind farm buildings when thieves broke into the cab and removed the unit from the dashboard.
Fortunately the manufacturer was able to replace the £11,000 guidance system within 24 hours, so only a day’s combining was lost.
However the theft from a combine that was hidden from prying eyes behind farm buildings - and the theft of a GPS system from a neighbour’s tractor the same night - brought home how vulnerable farms are to organised crime.
“It was clear that the thieves had done their homework and knew where the combine was parked,” said Mr Papworth, whose family's firm is based at Felmingham, near North Walsham.
“Over the last few years we’ve put in place more and more security measures to protect our farm machinery and tools, but it’s a constant battle to try and keep one step ahead of thieves who are very determined and quickly learn how to get round whatever we do.
“Nowadays we don’t leave machinery outside unless it’s impossible to get it back to locked farm buildings at night when possible.
“The constant threat of crime makes farming very difficult. We’re frightened to leave things out nowadays. We get fuel, tools, and batteries stolen if we do.“
Another north Norfolk arable farmer, who did not wish to be named, was shocked that a gang of thieves was able to take four expensive GPS systems out of tractors last August - from just 40 yards away from where his son was sleeping.
“I just feel absolutely sick to my stomach that people would come into our yard so close to my son’s house," he said. "The vehicles were all locked and somehow they forced the locks open without waking anybody up.
“It’s unbelievable how they could do it so quickly and quietly.
“The GPS systems cost in the region of £8,000 per machine. Since then we’ve upgraded the alarm system and the cameras at the cost of many of thousands of pounds. So there has been a financial cost but the main one is the emotional side of it."
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