document: Clare Mackintosh said it was "a dream come true" to see I Let You Go named best crime novel at the Theakston Old Peculier Crime Writing Festival.
  She beat five authors, including Robert Galbraith - the crime-writing pseudonym of Harry Potter author JK Rowling.
  Author Val McDermid was also honoured with an outstanding contribution award at the festival she helped to set up.
  Oxfordshire-based Mackintosh, who spent 12 years in the police force before leaving in 2011 to become a full-time writer, said she had been an unpublished author when she first came to the festival in Harrogate, North Yorkshire.
  "I would like to thank my publishers and agent for supporting me, everybody who has read and recommended I Let You Go, and the crime writing community for their endless encouragement," she said on Thursday.
  McDermid, a co-founder of the festival who won its best novel award in 2006, said it was "unlike any other in its warmth and generosity".
  The 61-year-old Scot said the outstanding contribution award meant "a huge amount".
  "This year sees the publication of my 30th novel and I can't think of a better way to celebrate that," she went on.
  Rowling congratulated her "friend and colleague" McDermid on her "justly deserved" award and said she had "been showing us all the way for a long time now".
  She added that the author's "favourable review" of her work as Galbraith had provided "one of Robert's proudest moments".
  "She received a thank you note in fake handwriting, only to receive one two weeks later in my real handwriting when I was unwillingly unmasked."
  Mark Billingham, another crime novel of the year nominee, called McDermid "the Queen of Crime", adding: "Long may she reign over us".
  McDermid, he went on, had "represented this genre quite brilliantly all over the world, both in person and through her novels, which have earned her legions of fans and a place among the very greatest crime writers of all time."
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summary: A former police officer's debut novel has won the Â£3,000 main prize at one of the UK's top crime-writing festivals.