To much of the world he was the inspirational leader who led Britain to victory in the Second World War, and one of the greatest characters in the nation’s history.

To Emma Soames, Winston Churchill was Grandpapa.

“I saw a lot of him in my early years,” said Emma. “But as I was becoming a sentient human being he was becoming a very old man. So I can’t say we sat and had long conversations about the Cold War. That did not happen! I was more interested in going with him to feed his goldfish and his budgerigars and his poodles.”

Emma grew up very close to her grandparents and saw a lot of them, but while she gradually became aware of Churchill’s historical significance she had no idea about her mother’s wartime role.

She will be in Norwich on Saturday October 29 to talk about discovering her mother's fascinating history and her own childhood memories of Winston Churchill, as part of the Hostry Festival.

Mary was Churchill’s youngest daughter and just 16 at the start of the Second World War and 17 when her father became Prime Minister. The family moved into 10 Downing Street and Mary’s teenage diaries were suddenly about air raids and world leaders (as well as friends and food and clothes and nights out.)

“It’s a massive honour and privilege for any child to read their mother’s voice from when she was a 16-year-old so I learned an enormous amount about her,” said Emma. “I didn’t really know she had kept these diaries during the war until she used a few extracts in her memoir which proved to be her last book.”

“I’m ashamed to say I wasn’t as attentive as I might have been to my mother’s past. To be fair to her, she was certainly not a war bore!”

“I didn’t know any of this before. She didn’t talk about it.”

Mary, who died in 2014, served with the Army in anti-aircraft batteries in London, Belgium and Germany, and accompanied her world-famous father to wartime summits and conferences as an aide-de-camp, meeting leaders including Roosevelt and Stalin.

“Diaries are a very teenage thing. The difference between my mother and others was that one she was a Churchill and Churchills believe in writing down everything, and secondly, she had such an interesting time,” said Emma.

“She was very unselfconscious in them, and sometimes rather silly! She was a teenager!

“She was so charming and so uncensored, ebullient and totally guileless. She writes about things like her scrumptious meals and her clothes and her weight and how she bites her nails.

“She’s quite hard on herself. But she always shows courage, and the one thing she always asks for is courage.

“In 1940 she is walking home from a night out in London and they cross Westminster Bridge and she flings a penny into the river and they make a wish and hers was for courage that it should never be lacking and it wasn’t. She was very cool about air raids.

“Her anti-aircraft battery was stationed in Hyde Park. And then of course there were the doodlebugs which were terrifying.”

Mary accompanied her father to the United States as his aide-de-camp in 1943, meeting President Roosevelt and staying in the White House, and to the 1945 Potsdam Conference in Germany where Churchill, Stalin and US President Truman helped draw up plans for post-war Europe.

But once the war was over Mary’s diaries were all-but-forgotten. She married and Emma said: “She became very, very busy. She had five children and my father [Christopher Soames who was also a Conservative MP] was a full-time job, really.

“He had a political career and she was at his side always and then they went to Paris. He was ambassador, so that was a full-time job for her. And then they went to what was still then Rhodesia. He was the last governor of Rhodesia and so all those moments would have been great if she had kept a diary but she didn’t really have the time.”

Emma, officially the Hon Emma Soames, said: “It has always been an honour to be connected to the family but when I was a teenager and in my early 20s I did rebel somewhat. I made a career for myself. I went into journalism and was determined never to write an article which had the word Churchill in it.”

Now a grandmother herself she enjoys writing about her illustrious family - and was so captivated by her mother's diaries that she has turned them into a book.

“I loved editing the book and people seem to want to hear about it, which is wonderful," she said. "I am looking forward to the Hostry Festival very much.”

She knows parts of Norfolk well because her brother, Jeremy, lives at West Barsham Hall, near Fakenham. Another brother was Conservative MP Nicholas Soames.

Her own career began in Paris, working for French Vogue, when her father was the British ambassador to France. When they moved back to Britain she joined British Vogue and then worked on the Evening Standard, edited the Telegraph magazine and then Saga magazine.

Since retiring she is delighted to have been able to revisit her own, and her mother’s, memories of Churchill.

“People are obviously very interested in her relationship with her father, as indeed am I, and she is wonderfully revealing about that in her diaries, and about her love for him,” said Emma.

“It turns out, reading between the lines, that when she was 16 she didn’t really know him very well. Then she goes to London and starts hearing his speeches and she says, ‘My love for my father is nearly a religion!’”

The 15 notebooks that Mary filled with her wartime diaries give an extraordinary and intimate insight into the personal and political life of one of Britain’s greatest national heroes.

Hear Emma Soames on October 29 as part of the Hostry Festival.

She will be talking to Guardian theatre critic Michael Billington about Mary Churchill’s War: The Wartime Diaries of Churchill’s Youngest Daughter in the Hostry, Norwich Cathedral, at 1pm, followed by a Q&A, book signing, and a talk by Michael Billington about his book Affair of the Heart, British Theatre from 1992 to 2020.

Hostry Festival patron and Oscar winning actress Hayley Mills talking about her new autobiography Forever Young on October 30.

The Hostry Festival finishes with the Norfolk Arts Awards on November 6.