Terry Pratchett had new Discworld books in the pipeline before his death

The Shepherd's Crown afterword reveals that sketches of stories were left behind

Terry Pratchett, creator of the Discworld series of books (David Sandison)

Terry Pratchett had "at least four" more Discworld novels in the pipeline before his death in March, the afterword to his last book The Shepherd's Crown has revealed.

Pratchett died aged 66 after a long struggle with Alzheimer's, leaving fans of his hugely popular fantasy series bereft. Crowds gathered at midnight bookshop openings last night to be among the first to get their hands on the late author's 41st novel.

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Readers may not have reached the afterword yet but in it, Pratchett's assistant Rob Wilkins writes that outline notes and sketches of stories were left behind - "just a few of the ideas his office and family know about," the Guardian reports.

One plotline involves "how the old folk of the Twilight Canyons solve the mystery of a missing treasure and defeat the rise of a Dark Lord despite their failing memories", which holds deeply personal connections with Pratchett's illness.

Then there's another idea featuring Constable Feeney of the Watch, who fans will remember from Snuff, "solving a whodunit among the congenitally decent and honest goblins". The ship's cat from The Amazing Maurice and His Educated Rodents was also in line for a starring role.

Readers hoping that someone else will pick up where Pratchett left off with these Discworld stories are likely to be disappointed, after his daughter Rhianna made it clear in June that she would not be writing them herself, or giving "anyone permission to do so".

Terry Pratchett with his daughter Rhianna in 1998 (Rex Features)

Rhianna, a video game writer, replied to a fan's query on Twitter, explaining that she will be involved with "spin-offs, adaptations and tie-ins but that's it".

"Discworld is his legacy. I shall make my own," she said.