Thieves waded across a river to steal £11,000 worth of GPS equipment from a tractor dealership near Woodbridge.

The men broke into the Ernest Doe agricultural dealership in Marlesford on the evening of Friday, May 7 and stole the valuable navigation equipment from four tractors and a combine harvester.

The stolen equipment was first thought to be worth around £24,000, but calculations show the figure is closer to £11,000.

The thieves were in and out within 40 minutes after wading across a small river to get into the dealership, according to branch and sales manager Tim Sheppard.

Mr Sheppard said: "They knew exactly what they were doing. They could get into the vehicle, I calculated, within about five seconds.

"They knew exactly what tools they would use or need to remove them.

"Rather than cut the wiring they actually unplugged it which was rather decent of them because the cable looms for those are in excess of £1,500 to replace."

Mr Sheppard said the thieves took GPS screens from inside the cabs of the tractors and the satellite receivers from the roof of the cabs that automatically guide farmers around fields.

He said thefts like this are becoming "exceedingly common".

Sergeant Brian Calver from the rural and wildlife team at Suffolk police said: "From our initial investigations these offenders are willing to go to great lengths to get what they want.

"Those responsible for this offence had a high degree of knowledge of how to access the site and how to access the units without any keys.

"I’d urge farmers, land owners and businesses that supply the equipment to stay vigilant to any suspicious activity.”

Mr Sheppard added that the most modern versions of the GPS equipment are coded to specific machines, making them worthless to thieves.

"They are specific to that tractor, they will not work on anything else," he said. "Now that's a new thing, but they are tuned in to the Engine Control Unit (ECU) of that machine.

"And therefore, if you plug it into a different machine which has a different ECU, it will just shut down."