Eliza Pakenham: The latest member of the Longford family to take up the pen

Her aim? To rehabilitate a long-maligned ancestor, Wellington's unhappy wife

the novelist Rachel Billington once remarked that she and her seven siblings were always disconcerted by being hailed in the press and at Foyle's lunches as "the literary Longfords". Growing up the children of the high-profile Labour Cabinet minister and prison reformer, Lord Longford, she said, had meant that they had always seen themselves as first and foremost a political family.

In her youth their mother, Elizabeth Longford, had been among the first women to stand for Parliament, but it was as a historian rather than a politician that she made her name, with celebrated biographies of the Duke of Wellington and Queen Victoria, and it seems to have been their mother's literary genes that prevailed with the Longford children. Thomas Pakenham and Antonia Fraser are both award-winning historians. Billington has published 20 novels, as well as children's books, while her sister Judith Kazantzis is an admired poet

In recent decades another generation has joined the family business. Sisters Rebecca, Flora and Natasha Fraser have all published works of history and biography, while their brother B H Fraser is a poet. This week Eliza Pakenham, the daughter of Thomas, the current and eighth Lord Longford (though he doesn't use the title), joins their ranks with her first book.

She is following in the family footsteps in more than one way, for Soldier, Sailor: an Intimate Portrait of an Irish Family takes as its subject her own ancestors. "My original idea," she recalls, "was to call the book 'Portraits on the Wall'. I lived for the first four years of my life at Tullynally [the Longford seat since the 17th century, a large, grey limestone Gothic Revival castle in Co Westmeath] and after that we would go there for school holidays. It was only in 2000, though, that I returned with my husband and sons to live full-time in Ireland. And so there I was at Tullynally, taking a look at the place where I was now going to be spending much more time, when I saw the family portraits in the dining room and the title came into my head."

Pakenham, pale, elegant and self-deprecating, a mother-of-three with the impeccable good manners of a bygone age, relates how she tried out the title on a literary agent friend. She got the thumbs up. She had previously worked in publishing in London , for Naim Attallah's Quartet imprint, and had even attempted a novel – "about the suffragettes, all very dashing" – which never made it into print. She worked the new idea up into a proposal that attracted a publisher. "The only drawback," she says with a gentle laugh, "was that they didn't like 'Portraits on the Wall'. Everyone thought it was a very bad title, not snappy enough, or fashionably short."

I'm not sure if they were entirely right, for it does neatly sum up the basic premise of a book that takes a similar approach to telling history to Stella Tillyard's Aristocrats. Using the family archives – of which more anon – Pakenham charts, through their letters to each other, the interwoven lives of some of those hitherto unnoticed family faces who form the backdrop to mealtimes at Tullynally. She focuses in particular on a group of siblings at the start of the 19th century. They were coincidentally also eight, and no less accomplished than her father's generation, though back then the male Longfords were military or naval leaders and the females tended to fall for men in uniform.

Catherine Pakenham, for example, usually known as Kitty, was the sister of the second Earl of Longford, and in 1806 she married the Duke of Wellington, conqueror of Napoleon. History's judgement of Kitty, her descendant believes passionately, is a "very shabby one". Kitty does tend to be presented as vain, foolish and a source of unhappiness and embarrassment for her husband. It was a perception that Elizabeth Longford touched on in her own life of Wellington.

"Another of the spurs for my book was a conversation I had with Granny about Kitty and the Wellington marriage," remembers Pakenham. "By then she was in her last days and living in a nursing home [she died in 2002 at the age of 96] and I said to her about Kitty that there must be more to it, that the story hadn't been told fairly from her point of view. And Granny just looked me in the eye and said, "You will be the one to do it." So then I felt even more determined.'

Later, as she searched Tullynally for material about Kitty and her siblings, Pakenham had, she says, a real sense of her grandmother watching over her labours. "Every time I found one of Kitty's letters, I felt in some way that I was paying homage to Granny."

Some of the long-lost documents that receive a first airing in the book were in very obscure places, both at Tullynally and elsewhere. Perhaps the most extraordinary find, Pakenham reports, was made in a Dublin attic. "My father had directed me to an old lady who was the widow of the family land agent at Tullynally. He in turn came from a line of land agents. She showed me these trunks she had, which were hidden behind some bookshelves and covered in soot. I had to drag them out and then, as soon as I opened the first one, on top I could see Kitty's writing on a bundle of letters tied with pink ribbon. They were letters to her sister, Bess. It was so exciting. I remember thinking, 'maybe no one has read these letters since they were first sent in 1815'."

At Tullynally too, some of the storage arrangements for objects relating to the family history were unconventional. "When we used to go there for holidays as children, it was always raining, so we'd play endless games of sardines. It was such a big house compared to what we were used to in London that you'd hide and then everyone would forget about you. I remember being left on my own looking in a trunk under a dusty cot in an old attic and coming across the uniform that one of my great great uncles had worn in the Crimean War. It was covered in dust. No one had put it away properly. And then in another cupboard were my grandfather's coronation robes. We used to dress up in them."

The Longford papers were, however, in rather better shape having been catalogued in the early 1990s, though since then, Pakenham reports, new piles have grown. "On the top at the moment are my grandmother's literary papers. And underneath them my father's. Layer upon layer." One of her ambitions, she reveals, is to try and digitise some of the archives, such as wage and tenant books, so they can be accessed by members of the public keen to trace ancestors who once lived or worked on the Longford estates.

First, though, there is the publication of Soldier, Sailor. Is she, I wonder, wary of the comparisons that will inevitably be made between her book and those of other "literary Longfords"? There's no trace of hesitation. "Not at all. Perhaps I should be. But if anything, I am pleased to be moving in their direction. And I have dedicated the book to my grandmother."

What of the portraits on the wall now? Do they feel more like friends rather than relics of an obscure past? "I've always felt a strong connection with Tullynally. I have always seen it as home. But now I feel that the whole place is absolutely embedded in me," she says. "I can feel my ancestors whispering over my shoulder." *

The extract

Soldier, Sailor: an Intimate Portrait of an Irish Family By Eliza Pakenham (Weidenfeld £20)

"...Sadly cracks were already beginning to show in this domestic peace. Arthur [Duke of Wellington] was constantly away, and Kitty was constantly making blunders. Her trouble was her tender heart, and lack of domestic economy: she lent a large sum of money to her insolvent brother Henry, paid out guineas to every charitable cause that came her way, and left household bills in arrears. It infuriated Arthur..."

Longford files: Key books from a literary dynasty

Wellington by Elizabeth Longford (1969 and 1972)

Two volume life of the soldier-statesman, still regarded as definitive

Mary, Queen of Scots by Antonia Fraser (1969)

The first of the critically acclaimed and best-selling works by the most popular historian of her generation

The Scramble for Africa by Thomas Pakenham (1991)

Prize-winning account of the 19th century rush to colonise Africa, its brutality and its consequences

The Unruly Queen: A Life of Queen Caroline by Flora Fraser (1996)

Feted biography of the woman George IV tried to prevent becoming his queen

Charlotte Brontë by Rebecca Fraser (1988)

A literary life that was praised as 'the best biography of Brontë since Mrs Gaskell's'

One Summer by Rachel Billington (2006)

The 20th novel by this enduring storyteller, who ranges widely in subject and style