Dairy farmer John Taylor tried to block the thieves' escape with a metal gate when he caught them stealing diesel from Church Farm in Sherbourne on October 1.

But the two men drove into the gate, knocking the 60-year-old man to the ground and fracturing his skull.

Mr Taylor and his sister are tenants on the estate owned by Warwickshire farmer Robin Smith-Ryland. Estate manager Dianne McDougall said the farming community was "appalled" by the act.

She added: "John's an honest man trying to do an honest day's work for the people of this country and we have callous people who care nothing about people like him."

Mrs McDougall said Mr Taylor's recovery was likely to be slow, but neighbouring farmers and members of Mr Taylor's family are helping carry out his duties on the farm.

She urged anyone with information to go to the police and not to confront thieves who had "no regard" for human life.

She added: "It's a warning to people to be vigilant, especially those who live in remote areas."

Warwickshire Police are appealing for witnesses to the crime or anyone who saw two white men driving a 4x4 and acting suspiciously in the area.

Anyone with information should call Leamington CID on 414111 or can contact Crimestoppers anonymously on 0800 555 111.

Agricultural insurance company NFU Mutual has warned country residents to protect oil and diesel tanks.

It said soaring fuel prices have led to a spate of red diesel and heating oil thefts from farms and rural homes, with 30 per cent more thefts than the first half of the year.

Thieves are also targeting central heating tanks in the gardens of rural homes.

As a result many farmers and homeowners are moving tanks and improving security measures such as floodlighting and alarms in their farmyards and gardens.

Spokesman Tim Price said: "This attack, and a similar incident in County Durham this year in which a farmer's wife died and her son was injured, show the lengths thieves will go to steal oil.

"Waking up to find thieves in their farmyards is becoming one of farmers' worst nightmares as they know how serious the consequences could be."

NFU Mutual has issued a security checklist for people with oil or diesel tanks.

* Deter thieves by installing lockable gates and by maintaining fences.

* Plant shrubs or install fences to hide domestic heating oil tanks from opportunist criminals.

* Check tank oil levels regularly.

* Install automatic movement sensor security lighting where possible.

* Consider moving easily accessible tanks to a better protected area or building.

* Note suspicious vehicles' registration numbers and report them to the police.

* Ensure tanks in outbuildings or sheds are kept locked.

* Remove empty containers or drums from the area around tanks.