The video (and Koenigsegg testimony) confirms that Lilja built up to the target speed gradually - or up to around 190mph at any rate - before full throttle and a lo-ot of road finally delivered 284.55mph on this, the quickest run of the day. Given the "undulating" nature of the highway (Koenigsegg's description) we rather think he earned the fist pump at the end.
As well as setting the highest top speed for a production vehicle - 277.87mph, the average of two runs in the opposite direction - Lilja and the RS set four more world records that morning: 0-400-0 km/h, a flying kilometer on a public road, a flying mile on a public road and the highest speed achieved on a public road.
Interestingly, the flying kilometre had apparently stood for nearly 80 years, having been set in 1938 by Rudolf Caracciola on the Autobahn between Frankfurt and Dormstadt aboard a modified Mercedes W125 racecar. That he managed an average speed of 268mph on thirties era tyres does rather require a solemn doffing of the cap.
Koenigsegg - as we've previously reported - stuck with the RS's standard Michelin Pilot Sport Cup2 rubber, and only used one set of tyres to achieve all five records. It was also a customer car, albeit one fitted with an optional roll cage and the 1MW engine upgrade which extracts 1360hp from the 5.0-litre V8 when running on E85 fuel.
The owner of the car - along with other US-based Koenigsegg buyers - was responsible for facilitating what the company calls a "massive logistical exercise" which of course included closing a significant amount of not completely flat Nevada highway. An 11km stretch which now goes into the history books alongside the remarkable Agera RS and its unflinching pilot.