Koenigsegg has revealed that its One:1 “megacar” has managed to accelerate from a standstill to 300km/h (186mph), and back down to zero again, in just 17.95 seconds.

Sounds fast, right? It is fast. Way back in 2011, its Agera R set a bona fide Guinness World Record for the same 0-300-0km/h acceleration-deceleration time, clocking a piffling 21.19 seconds.

Related: How do we get to 300mph?

Which means the 1,340bhp, Agera R-based One:1 is a full 3.24 seconds quicker than its predecessor. Perhaps most enlightening is that the run was conducted with ‘Segg works driver Robert Serwanski showing us the sheer stability of the thing by taking his hands off the wheel. At 200mph.

The record-beating acceleration and deceleration tests were conducted at a practice session – yep, they weren't even gunning for the record, but just going for a little stretch – at Koenigsegg's test track in Sweden.

You want the full set of stats? Zero to 300km/h took 11.92s. 300-0km/h took 6.03s. The One:1 went from zero to 200mph in 14.3s, and braked from 200-0mph in 6.384s.

The development car used (there are six production version to follow, as Top Gear exclusively told you last year) was also 50kg (110lbs) heavier than “standard”, thanks to a roll cage. And, to cap it all off, Christian von Koenigsegg reckons the car can go faster still.

A version of this story originally appeared on TopGear.com.