The protestors struck after the trial had been completed

It comes several months after it stopped carrying out GM tests.

Holme Farm at Spital in the Street, Lincolnshire was the focus of furious protests in 1999 while it trialled controversial genetically modified crops.

Then the wrong field was targeted by 46 people who were eventually charged with conspiracy to commit criminal damage.

This time anti-GM graffiti was sprayed on farm buildings and an electric fence cut.

The farmer said that it could have put his animals at serious risk as it left them free to wander onto a busy main road.