Pottering around his garden, listening to classical music and playing with his grandchildren is hardly the image you would conjure up of the man who is strategising on how to fight one of the toughest general election battles in decades.

Yet Lord Paddy Ashdown reveals when he isn’t donning his political cap and leading the Liberal Democrats 2015 general election brigade he most enjoys spending time with his family in Yeovil – the constituency he once represented as an MP.

“When I’m off, it’s my garden, it’s my music and it’s my grandchildren,“ says the grandfather-of-four who was knighted in 2000.

But it’s clear the 73-year-old, who led the party from 1988 to ‘99 and whose marriage survived his infamous ‘Paddy Pantsdown’ affair, has not completely softened with age and still knows how to wield his political diplomacy.

He spoke to us on the day of the European and local elections and when asked about UKIP leader Nigel Farage, remained tight-lipped, only adding he has met all the political chiefs, but cannot recall what he and the controversial politician discussed.

One topic Paddy (as he prefers to be called) doesn’t have trouble talking about is his latest book, The Cruel Victory, which depicts the hidden story of the D-Day landings, which took place nearly 70 years ago.

Paddy’s first book, A Brilliant Little Operation, told the story of the Cockleshell Heroes who paddled canoes into Bordeaux Harbour to sink German ships.

He will be at Hawthorne Theatre next week to talk about his new novel, which was more than three years in the making and required reading in excess of 60 French books.

Paddy says: “It is the hidden story of D-Day. Everybody knows what happened on the beaches, they know the position of almost every last soldier but nobody knows what happened behind the lines when hundreds of thousands of Frenchmen were told that the hour of liberation had come and that they were to stand and fight.“

The Cruel Victory focuses on the two groups of people who made D-Day successful; the Allied troops who assaulted the beaches and the French who fought to put the Germans off balance.

Hours were spent trawling the National Archives at Kew, as well as the French National Archives, and the former Lib Dem leader took the opportunity to write everywhere and anywhere.

Paddy says he has chosen to release his book now because this month is the 70th anniversary of the landings.

Although his two books have focused on military history during one of the bloodiest conflicts in history, Paddy says that one of the biggest misconceptions people have about him is that his time spent in the Royal Marines and Special Forces was the most important part of his life.

He says: “Everybody says ‘Paddy Ashdown, ex-Royal Marine, ex-Special Forces’, but actually that is the least important part of my life. They never say ‘Paddy Ashdown, ex-unemployed, ex-youth worker’, but I was those too.

“So, being in the military was part of my life, but only part of it and its influence on it is not nearly as great as people think.“ Nonetheless, it’s easy to get swept away with Paddy’s extensive experience. The man himself admits that he has always liked to remain incredibly busy, explaining that he “hates free time“.

He adds: “I’m always doing something. My wife tells me that this time of our lives is when I pretend to be retired and she pretends to believe me, so I hate being idle.“

Even Paddy’s writing is slotted into the “little corners“ of his life, he says. Whether the location be sitting at the House of Lords late at night, waiting for a vote to take place, or merely an opportunity to pass the time before boarding a train or plane, Paddy writes wherever he can.

The three years it took to complete this book has not deterred Paddy from writing another book, who says he already has some ideas in mind.

In the meantime, it’s off with the slippers and time to take helm of the Lib Dems General Election Campaign, which Paddy confesses is “going to be tough“ and “a big task“.

Hawthorne Theatre, The Campus, Welwyn Garden City, Tuesday, June 10, 7.30pm. Details: 01707 357117, hawthornetheatre.co.uk