Madness are the latest names confirmed for this year's Camden Crawl, playing a series of secret shows at the festival.
The ska legends are set for several free performances on Friday 24 April for which Camden Crawl tickets will not be required for entry.
Head of BBC 6Music Jeff Smith, who are putting on the secret shows, commented: "6 Music are delighted to bring Madness back to their spiritual home to give a performance that truly connects them to their home crowd and to the wider 6 Music audience."
One listener will have the opportunity to play with Madness. Click here for more details.
Camden Crawl 2009 will take place around various venues in Camden, north London from 24-25 April.
Billy Bragg, The Maccabees, Yeah Yeah Yeahs, Echo And The Bunnymen and more are also set to perform.
Tickets are still on sale priced at £54.81 for a weekend pass or £32.79 for either a Saturday or Sunday pass.