One of Rhianna Pratchett’s most cherished early memories is of tucking herself “like a human hot-water bottle” at her father’s back in the big chair in his study, “peering out from behind him” as he played computer games.



The year was 1982 and Rhianna was six. Her father, Terry, was a young science-fiction writer who would the following year publish The Colour of Magic, the first in the bestselling Discworld series that would see him become one of Britain’s most successful authors, second only to J K Rowling.



Those hours spent in front of the computer with her father had a lasting impact on Rhianna, who went on to become a successful writer of video games, known for her work on Tomb Raider, Heavenly Sword and Mirror’s Edge.



“I was interested in what my dad was interested in – robotics, gadgets and computers,” she says. “I thought that fighting aliens and robots was something that girls did as well as boys, so I found a way of doing that for a living.”

And now, following her father’s untimely death at the age of 66, she has another role: guardian of Discworld – the fantastical, hilarious, endlessly surprising milieu that Sir Terry devised. It is loved by millions the world over, from children who delight in the daft humour and silly puns to academics who relish the sharp satire and social critiques (there is at least one serious philosophical volume examining the epistemological and existential implications of the novels).

Sir Terry announced in 2012 that he would be leaving the intellectual rights for Discworld to Rhianna, and father and daughter launched the multimedia production company Narrativia to retain exclusive rights to his work across all platforms. With sales of tens of millions of books worldwide, it is a massive empire.

“My role will be to protect the brand that Dad has established,” she says. “I will steer Discworld. I will be a caretaker and look after how it’s used and adapted.”

For Rhianna, who announced Sir Terry’s passing on Twitter in the voice of Death, one of his best-loved characters, her father was always a kindred spirit. They shared, she says, the same imagination, a sense of impatience and a fondness for witty sarcasm.

“I just always ‘got’ Dad,” she says. “He always had this desire to share experiences; it was the way he was brought up himself, so he would talk to me as if I was on his level and he made a literary confidante of me pretty early on.

“Dad was like a druid: he taught me how to build watermills in the stream, the names of plants and flowers, and what was edible in nature. It was like growing up in Middle Earth and having a full‑sized hobbit for a father.”

Rhianna Pratchett with her father, Terry, in 1998 Credit: REX/ALEXANDER CAMINADA/REX/ALEXANDER CAMINADA

She recalls when she was very young being woken by him in the middle of the night, wrapped in a blanket, and taken outside to see the glow-worms in the hedge.

“He felt it was more important that I experienced the wonders of the world than got a good night’s sleep,” she says.

Rhianna – the only child of Sir Terry and his wife Lyn, a former art teacher – was raised in rural Somerset where, in another indicator of her parents’ somewhat unconventional approach to parenting, she was possibly the only little girl to have a 6ft picture of the terrifying Alien Queen from the Alien films pinned to her bedroom door.

She was also probably one of Somerset’s best-travelled youngsters. Between the ages of eight and 16, her parents took her with them all over world when her father spoke at fantasy and science-fiction conventions.

When at home at the family’s pink hillside cottage, one of her favourite pastimes was to climb a tree and read a book. “It was all very Heidi-like,” she says, recalling how her father – who kept ducks, chickens and goats – would allow her to herd the latter through the valley, watching from a distance.

At our interview, which took place some time before Sir Terry’s death, it was obvious that Rhianna was very much her father’s daughter. The novelist favoured a look once described as “urban cowboy”, almost always topped off with a large black fedora. His daughter has what she calls a “business Goth” style, which comprised a slinky black trouser suit, pointy-toed black stiletto boots and a red and black T-shirt from the slightly outré “rave-wear” retailer, Cyberdog.

She also sported a Batman knuckleduster and a silver skull pendant that, she explained, was modelled on Discworld’s Death. In the novels, Death always speaks in capital letters, as in the tweet that Rhianna sent, with shaking hands and tear-filled eyes, last week: “AT LAST, SIR TERRY, WE MUST WALK TOGETHER.”

But Rhianna and I also talked about the more mundane lower-case death, which her father was then facing with great courage. In 2007, at the age of 59, Sir Terry had outed himself in a press release to the world as an Alzheimer’s sufferer. He wanted to raise the profile of the illness that he described as an “embuggerance”.

Rhianna told me: “That didn’t surprise me – it felt like the right way for him to deal with things. We Pratchetts are a bit ‘fighty’ – you don’t change anything by staying quiet.”

But she also admitted that “it was devastating when I first found out about Dad’s illness and it took a long time to sink in”.

“I try to be a glass-half-full person. There will always be those glass-half-empty, dark-night-of-the-soul moments, but it’s about keeping up that fight, I think.”

She was in a taxi to Heathrow for a work trip to the States when her father rang to tell her before he went public. “It took me five attempts to fill in my US visa form because I couldn’t focus. I even burst into tears in front of the cabin crew. My parents and I have always been a very tight little unit.”

It was an odd experience, she said, to have the world knowing about her father’s condition, having to field questions about it on Facebook and Twitter. However, she grew even closer to both parents after her father’s diagnosis. She said that the family was “just trying to get on with it in that very British way”, but that all three had become more emotionally open, which was “a silver lining for a cloud that I’d rather didn’t exist”.

Her parents were living in Wiltshire, while she was based in London but they saw a lot of each other and spoke constantly. “I’m always telling them I love them on the phone in a slightly silly way. We always say to each other, ‘Mind how you go’; it’s almost like a Pratchett mantra for safety.”

Her mother was a tower of strength, she said. “She’s a very generous spirit, kind and caring. They have been wonderful parents: very good about not nagging me to have kids or get married. It’s like they missed out a chapter in the parenting manual.”

After his illness was announced, father and daughter sometimes worked together on Discworld stories (they also worked on a soon-to-be-made TV version of his series The Watch). The result, she told me, was that her father addressed her as a fellow writer. “It’s lovely working on characters and biographies and reading them out to him and him laughing at a joke that he thinks is his – but is actually mine. If I can make my dad think one of my jokes is his, it really has to be the ultimate compliment.”

Sir Terry’s rare early-onset form of Alzheimer’s, posterior cortical atrophy, meant that he couldn’t type or drive or dress himself without help; he wrote with speech-recognition software. In several BBC television documentaries, he talked frankly about his wish to use the assisted‑dying organisation Dignitas when the time came.

I asked Rhianna about her views on assisted death. “I absolutely support everything he has done to champion Dignitas,” she said. “Yes, it was hard for me to watch the documentaries, but I saw the importance and the value in them to get people talking.

“We do have a problem with talking about death and last wishes in this country, yet we are all going to die – and we should be able to talk about that in a mature, adult way.”

Last week Rhianna tweeted a picture of herself with her father, saying "Miss you already". It's a sentiment shared by millions.