On the 30th anniversary of the first publication of The Hitchhiker's Guide To The Galaxy by the late great Douglas Adams and the eve of the release of a brand new addition to Adams' legacy, this is a day of celebration, spectacle and delight voyaging deep into the Hitchhiker's Universe.
Start the day at a photocall of the largest number of Hitchhiker fans ever (11.30am on the riverside terrace). Remember to wear your dressing gown and bring along a towel.
At 1.30pm in the Clore Ballroom there's a mega-signing of the new editions of the first five Hitchhiker novels.
And at 5.45pm you can buy the new sixth book in the series a day before everyone else and get it signed by Eoin Colfer.
Many other out-of-this-world events and entertainments throughout a day devoted to H2G2 â€“ including special free screening of the Hitchhiker series in the Clore Ballroom.
Plus a number of ticketed events in the RFH itself.