The news came from an article on bbc.co.uk the 24th august about BBC Four's new season : "Dirk Gently, the bumbling detective creation of The Hitchhiker's Guide to the Galaxy author Douglas Adams, will come alive on the screen for the first time in a mystery that stems from his attempted rescue of a cat from an old lady's house."
Then, the day after, guardian.co.uk published an article with some more informations : "BBC4 will also dramatise Adams's 1987 novel about anti-hero Dirk Gently next year. Adams was writing a third Dirk Gently book, The Salmon of Doubt, at the time of his death in 2001.The books have formed the basis of a play and a BBC Radio 4 series but have never before been filmed for TV. ITV Studios is shooting a one-off pilot for BBC4, adapted by Misfits creator Howard Overman."
James Thrift, Douglas Adams' brother, wrote on the DAC forum, that "I (too) had reservations, until I saw the script. Good feeling about this one."
Many thanks to DaveH from the ZZ9 Plural Z Alpha fan club for this incredible news.