A few months ago, Mr Koenigsegg dispatched one of his Agera R hypercars, a driver with a lead foot and a tracking box to a proving ground in Sweden. Said driver performed some lightly astonishing feats of acceleration. Six, to be precise.That last one is significant. Yesterday, Mr Koenigsegg got the call from Guinness: "The fastest time for a two-seater production car to travel from 0-300-0 km/h is 21.19 sec, achieved by a Koenigsegg Agera R, driven by Robert Serwanski, at Angelholm airfield, Sweden."There you have it. It is officially a speed demon. With magnificent brakes.