Ship's log, Roi des Belges: Sunday 15 January, 2012. Time: 4pm. Weather: fine. Wind: south-westerly.
Crew safely on board and feeling very pleased with themselves, standing on the top deck sipping prosecco and waving at promenaders on the South Bank as they admire the Thames river views from Big Ben round to St Paul's. It has been an unusual embarkation, via a backstage door at the Queen Elizabeth Hall and up a specially installed lift to the roof.
Resembling a 1920s steamer and designed by architect David Kohn and artist Fiona Banner, the Roi des Belges interior is red-stained plywood with not a nautical blue and white stripe in sight. The spacious main deck's bow is lined with windows and a wraparound wool banquette. There's a massive bed, which cleverly converts into twin beds by sliding on runners built into the floor.
Behind is a table and chairs next to a kitchenette. A shower room and toilet – with portholes giving views of St Paul's or the London Eye – straddle the entrance hall at the back of the boat, or "stern".
The pièce de resistance is the snug upper deck, filled with London-themed books, which we quickly rename "The Bridge" and where we write up the ship's log. This weighty tome is where guests who managed to secure a night's stay when bookings went live last September (six months' worth of bookings snapped up in 12 minutes) are expected to chart their experience. Fountain pen provided.
Alain de Botton is the philosopher behind Living Architecture, the foundation which rents out unusual holiday homes and came up with the idea for the project. He put "demons", as his 3am log entry under the heading "sightings" when he stayed earlier this month. Our entry for the same hour reads: "Man, singing loudly, zig-zags across Waterloo Bridge".
Later this month, the boat will host its first "artist in residence", the multi-instrumentalist Andrew Bird who will play a one-off gig via live webcast (28 January). Other musicians such as David Byrne and Laurie Anderson will also perform, and writers including Michael Ondaatje and Jeanette Winterson will take part in A London Address there, a series of monthly writings and recordings .
We use our binoculars to study the faces of those beneath us on the South Bank: lovers, strollers, joggers. We are constantly drawn to the "vessel" opposite. As night falls, the opulent Savoy hotel lights up like a jewelled beacon, its crystal interiors shining out over the inky Thames.
Ship's log: 5pm. A police launch, its sirens blaring, speeds along the water, dodging the packed tourist boats. Trains rattle over Hungerford Bridge, snatches of conversation drift upwards, a saxophone wails plaintively.
Ship's log: 11.26pm. Crew retires for the night. Blinds are left untouched, but sleep doesn't come quickly. We keep sitting up and looking out at London's multi-coloured riverside.
Monday, 16 January. Ship's log: 7am. the sun has just risen. On the starboard side, The Shard pierces a pinky red sky.
Ship's log: 11am. Binoculars stowed, log up to date, crew disembarks, wishing their "trip" could have been longer.
• Be warned, the first sale of nights in the boat, for between January and June, sold out in just 12 minutes. Bookings for July to December will go on sale online this Thursday, 19 January, at midday GMT. A Room for London (aroomforlondon.co.uk, living–architecture.co.uk) sleeps two and costs £300 for a night, one night maximum
