Rave outdoors all day, disappear into a sweaty club when it gets dark, dance all night and emerge blinking into the milky sunshine of the next day. That's the proposition Sunfall presented earlier this year, when it announced a smartly curated debut line-up featuring Jamie xx, Kendrick Lamar-affiliate Kamasi Washington, dubstep reprobate Zomby and nine different after-parties.
The main event takes place in south London's Brockwell Park and begins with lunchtime sets from New York whizz Anthony Naples and gloomy bass man Shackleton. Unfortunately for them, most of Sunfall's crowd are in snaking queues by the gates, still at the pub or having their faces slathered with glittery facepaint under some trees near the toilets. Zomby - known for frequent no-shows - turns up and pulls a bigger crowd, even if his housey set feels slightly flat. On the main stage, Kamasi Washington and his band are far from flat, drowning out any bass bleeding from the tents with jazz that slips from soft and smoky to wild, lavish and loud. Crisp and booming chunkily through the speakers, it sounds brilliant. Man-mountain Washington's sax leads the way, but there's a lot of fun to be had following the relentless meandering of his two bass players, particularly during 'The Rhythm Changes'.
By now Sunfall's heaving, and most of those present have clearly visited the facepaint stall and said "Make me look like a mermaid". Many are wearing sunglasses too, and the droves climbing the hill towards the main stage as Moodymann gets going advance like uniform rave droids. The Detroit techno head is disarmingly smooth, lamenting the fact that the bouncers won't let the audience join him onstage so he can "pour y'all some shots". They have to stick with shuffling sweatily down the front instead, but no one minds at all.
Indeed, no one really seems to mind anything by this point. Evening is setting in and things suddenly feel very loose. There's a big group taking turns to run and then deliberately trip over on the floor, and it's tempting to wonder if they're disturbing those patiently queuing for craft beer (£6.50 for a tasty but pocket-rinsing pint). The toilets are behind the beer van and, in contrast to the smiley atmosphere everywhere else, a weird silence hangs in the queue, broken only by the guy making bad jokes about Brexit and the urinal that springs a leak and turns into a jetstream.
Carrying on past the loos to the North Stage is rewarded with bruising techno from Joy Orbison back to back with Job Jobse and a headline set from another Detroit hero, Omar S. The levels are spot on again - the festival notably informed punters about its commitment to achieving the best sound possible before the event - and the tent is throbbing.
Outside, the sky is suddenly glowing orange and pink - we've been blessed with the kind of sunset that makes people want to stop to Instagram the outline of The Shard (you can also see Canary Wharf and all of The City from up here) on their way to see Jamie xx. Still riding the wave of last year's debut 'In Colour', he's got prime position - headlining as the sun falls on Sunfall.
Like that record (and indeed everything else this avid student of sound seems to do) his set is subtle, stylish and knowingly good. Jamie xx knows how to (politely) work a crowd and has an expert way with space, momentum and a good hook. But after a year on the road, you know precisely what to expect: hushed beats that elicit nostalgia, melancholy and euphoria delivered with elegant finesse, with the only potential variable being the colour of his shirt. It's black tonight, but sometimes it's white. Here he fills the role of dance music butler. A well-turned out man serving expertly crafted morsels of expensive-sounding bass and then disappearing, almost apologetically, with a bow of his tousled locks.
Jamie's next stop is The Coronet in Elephant & Castle, where he's having an afterparty. He then pops round the corner to have a dance at Corsica Studios, which plays host to BBC Radio 1 DJ Benji B's Deviation do. This dingy old club is one of the city's best and tonight it feels like a house party. There's a guy dressed all in fur and it's like everyone knows each other. The majority jostle and wobble in the main room, where a boisterous Zomby precedes Benji B and Moodymann. Playing in the smaller second room, Anthony Naples suffers another tiny crowd, but he'd probably be next door too if he could - the atmosphere is intoxicating. It has been all day.