Patrick Janson-Smith, one of the most popular figures in modern British publishing, has announced he will retire next autumn.

Janson-Smith will step down, closing his Blue Door imprint at HarperCollins U.K., after attending his 40th Frankfurt Book Fair. He has been in the business for 50 years.

His golden years in the trade were spent at Transworld, where he set up the Black Swan imprint. After a slow start, Black Swan went on to publish bestselling titles by Mary Wesley, Joanna Trollope, Bill Bryson and others. He also published books at Transworld by John McCarthy, Jilly Cooper, Terry Pratchett, Armistead Maupin, John Irving, Andy McNab, Robert Goddard, Sophie Kinsella, Mo Hayder, Howard Jacobson, David Eddings, and Frederick Forsyth.

Janson-Smith, son of agent Peter Janson-Smith, started his career at University of London Press (Hodder & Stoughton), and went on to work at Granada Publishing, Octopus and the Nationwide Book Service before joining Transworld as Publisher in 1981.

He left Transworld in 2005, and worked for a while as an agent with Christopher Little. The move was not entirely happy, and he joined HarperCollins to set up the Blue Door list in 2008. His authors there have included Maggie Shipstead, winner of the 2012 Dylan Thomas Prize. However, his many friends in the trade have sensed that in recent years he has not gained as much enjoyment from his work as he once did. Janson-Smith, who's always taken his publishing seriously but not himself, was a more-than-willing participant in any publishing fun: he was a stalwart of the once-annual Publishers' Panto, frocking up to play the Queen and Princess Diana (his legs were much admired!) and, on one occasion - with Liz Calder as Margaret Drabble and Paul Bailey as the interviewer - A S Byatt.

Janson-Smith said: "It feels rather sad to be shutting the door, both literally and metaphorically. However, it's high time this unreconstructed dinosaur waddled off and munched on the grasslands of Happy Memories. I've had fun and feel immensely privileged to have walked among so many authorial giants. And you know what they say - when one door closes, another opens. Maybe now I'll have time to write my memoirs."

HarperCollins CEO Charlie Redmayne said: "Everyone at HarperCollins will be immensely sad to see Patrick retire. He has had a wonderful career in publishing which is based on a real passion for books and writers. We will miss him here both professionally and personally and wish him well for the future."

Kate Elton, Publisher of HarperFiction, said: "It's been a privilege to work with Patrick at HarperCollins. His eye for talented writers and great storytelling has brought bestselling, award-winning writers to the HarperFiction division and he will be much missed by the whole team."

Janson-Smith will leave Blue Door on 31 October.