Investigators say the cause of a huge field fire - which destroyed 50 acres of land - is not known.

Kent Fire and Rescue Service today confirmed the start of the blaze which obliterated farmland in Lenham Heath has been classified as unknown.

Eight fire engines were sent to the scene and crews fought the flames for more than 90 minutes on Sunday afternoon.

The blaze was so large that it was said to be visible to motorists on the M20 between Junctions 8 for Leeds Castle and 9 near Ashford.

Andy Barr, farmer and landowner of East Lenham Farm, thanked his neighbour Bill Alexander for using his tractor to cut the crops when the wind started to push the fire towards nearby properties.

Speaking to KentOnline after the incident, Mr Barr said: “It was quite a big chunk – around 20 hectares (50 acres) of land was destroyed.

“There might be one hectare that we can salvage from that, but it will be pretty damaged anyway.

“It was meant to be going for malting barley, to go into brewing for beer. The prices for it are worth more this year than it has been for many years, due to other problems in the world.

“The main thing for me was that it didn’t go anywhere else – it was quite close to my brother’s house, and at one stage the wind changed and his property became engulfed with thick smoke.

“We have had little things similar to this before, but nothing like the standing crop suddenly going up in flames. Not on that scale.”

The farmer says the technique of ploughing the crop for fire prevention is an old method.

“That’s tried and tested, Bill kind of knew what to do straight away,” Mr Barr explained.

“There might be one hectare that we can salvage..."

“When I was younger we used to burn straw on purpose, to help the planting of the next crop and to get rid of weeds.

“You would plough all round the outside first and once you had turned the soil over, there was nothing to burn.”

He added the cost of the fire to the farm's business was not known until agricultural insurers visited to assess the damage.

A spokeswoman for the fire service said: "The cause has been recorded as unknown."

Officials confirmed no one was injured during the incident.