I am not the first hack to beat a path to John Gadd’s Fontmell Magna door. A few weeks back he was ambushed by the nationals who, sensing a Silly Season story, asked: “Is this The Most Boring Diary In Britain?”, presumably basing their judgement on just a few lines from the four million words John estimates he’s written over the years.

Oh foolish people.

Because John’s diary is a possibly one of the greatest and most sustained records of life in this part of the world that we have ever seen. There are more than 150 volumes and 33,000 illustrations covering everything from John’s work (he’s an internationally recognised pig consultant), to the birth of little Prince George.

And he only started it in 1970.

“Like many people I started a diary when I was young and my goodness, I wish I’d kept it up,” he says.

“It was the usual stuff, ‘got up, had breakfast, went for a walk’, boring! So I gave it up.”

All diarists feel like this, he says. “It’s like slimming, you start off full of enthusiasm and then it gets to be a pain.”

However, because of his work – he was meeting 400-500 people per year and needed to keep track of them all — he rebooted the project and started it as an aide-memoire.

“That got me going and kept me going over the second year,” he says.

Lifetime diarists, he says, always tell you it stops in the second year, so he persevered.

“By about year four the realisation begins to dawn that a lot of work and discipline has gone into it and that it seems a pity not to write an honest record of feelings, warts and all,” he says.

By years five to six he had started to include illustrations and after that, he says, it became “A complete obsession”.

It must be, because he has indexed it all, and can find any photo (like the ones of Fontmell’s VE Day celebrations), drawings (like the one he did of the book-strewn living room of the antiquarian dealer John Rushton) or comments on news stories of the day.

Like this one, from November 22 1990. ‘So Mrs Thatcher has resigned. Yes, it is sad, but sadder still that she got so self-confident, obdurate and out-of-touch that she brought it on herself... We watched her final debate and she gave a bravura performance and went out with guns blazing. All the more pity that this marvellous woman has alienated so many people like me.”

Or this, on April 29, 2011. “A Red Letter day not only for the wedding (William and Kate) but because we asked friends and neighbours to come and watch it on the telly – Barbara laying on a lovely ‘lap luncheon’... the hymns the couple chose were good but the much-lauded special anthem was totally tuneless. The camerawork from the BBC was stunning.”

But he has also recorded moments of extreme local significance, such as the floods which hit Blandford during 1979. John took the time to draw a map of where the waters hit.

“As far as I know this the only map of the extent of the floods,” he says.

“I suppose the council were too busy sorting everything out.”

He has also recorded 27 village fetes in Fontmell Magna. But some of his most interesting recollections are not part of the official diary at all.

John remembers one day in June 1944 when he was holidaying in Bournemouth and he woke up and felt strangely drawn to the Overcliff drive and the sea. There was a police road-block but John slipped through a few private gardens to be greeted by an incredible sight: “The whole bay from Studland to Hengistbury Head was covered in hundreds of grey ships,” he says.

“It was the most astonishing sight I’ll ever see; I think I could have walked between the ships there were so many of them.”

He quickly realised what it meant – that the Allies were about to launch their invasion of France – and after being caught by a policeman and warned not to breathe a word, he kept quiet until the next day when he returned to discover all the ships had gone.

Perhaps his best memory is of meeting Winston Churchill himself, at the Lord Mayor’s show in 1946.

“My father was a senior Army Officer and I had been invited there,” he says. “At one point an official beckoned me aside and asked if I would like to meet Mr Churchill, who was attending. Of course I would – he was my hero.”

John was surprised to discover the Great Man was much shorter than him and had red hair; “Which you didn’t see in all the black and white photos.”

Churchill was ‘very friendly’, asking him what school he attended and the subjects he enjoyed, which were geography and history.

“That’s good,” rumbled the former premiere.

“We can learn so much from history.” After chatting about mathematics, another official called upon Churchill to speak to an ambassador.

“Churchill turned to the man and said ‘Yes, in a minute, I’m speaking to this gentleman’,” says John. “Then he gave me a wink and had to go.”

So what is the future for John’s diary? Surely universities and museums are fighting over who will own it one day?

Apparently not. Well, not any British ones, anyway. “I’ve contacted the British Library and one or two universities but the response has been ‘very interesting, maybe’,” says John.

Two American universities, however, are desperate to acquire John’s life’s work and well they might.

“You really must be one of the UK’s most prolific diarists ever,” I tell him. John looks genuinely surprised. “I suppose I might be,” he says.