www.motor1.com/news/724812/mercedes-amg-one-215-mph-autobahn-video/
There, the car was able to reach a maximum speed of 347 km/h (215 mph) before having to slow for traffic.
347 km/h in traffic, WCGW
To be fair, I've not been TOO far off that speed myself in Germany and in the right circumstances it feels.... remarkably unremarkable
When you have roads that can handle 300+kmh as a matter of course, 347kmh in an AMG One is going to be super easy and nothing.