He is the record-breaking bullock that just keeps getting bigger and next week, the mighty Field Marshall, will be throwing his weight around an agricultural show to do his bit for charity.

The seven-year-old Charolais stands a towering 6ft 3in tall, dwarfing his owner Arthur Duckett, 78, and almost every other farm animal in the land.

The king of the farmyard was heavier than a Mini Cooper car when he was last weighed in but has piled on the pounds and beefed up even more since 2007.

But his exact weight will remain a closely guarded secret until Monday afternoon when all will be revealed. Field Marshall is taking part in a charity Fatstock agricultural show at Sedgemoor Auction Centre near North Petherton throughout the day and visitors are invited to pay £2 to guess his weight. The victor will receive a tonne of cattle feed or the cash equivalent.

The event has been organised by Burnham Rotary Club to raise cash for the SURE appeal and will go towards a new oncology unit at Taunton's Musgrove Park Hospital.

Mr Duckett, who bought the beast three years ago and keeps him on his Alstone farm, near Burnham, said: "I can't tell you how much he weighs right now but he has, without doubt, put a lot on since last year.

"When he is at the show on Monday, it will be the first time he's been indoors since he went 12 months ago so I'm not really sure how he will feel about it.

"But it is all for a good cause so people don't have to go all the way up to Bristol for cancer treatment."

The whopping Field Marshall spends his days outdoors and munches his way through 35lb of food, including oats, hay, sugarbeet and barley, every morning.

Mr Duckett said: "Because he is outdoors all the time, he gets a lot of exercise and is in good shape and health, he could live for another 10 years or longer. He is only fed once a day but he does get through a lot of food.

The ravenous creature's insatiable hunger has taken his weight beyond that of his former stable-mate and record holder The Colonel, who weighed 1.59 tonnes.

"He's still getting bigger," said a proud Mr Duckett. "He's definitely heavier than The Colonel now which makes him the biggest in the country.

"The first bullock I had was Captain, then we had The Colonel so I had to call this one Field Marshall after Field Marshall Montgomery because he's the biggest of the lot," he said.

Mr Duckett will use a lorry to transport his beloved pet to the show and hopes Field Marshall will be in good spirits.

Field Marshall will be greeting his public at the auction centre from 8am on Monday and his weight will be revealed at 3.30pm.