According to BridgeToGantry.com, a P1 set a laptime of 7 minutes and 4 seconds at the 'Ring. For those of you that lose track of other lap times, because well frankly there's too many, the closest road-legal cars are the Gumpert Apollo and the Viper ACR, achieving 07:11.1 and 07:15.6, respectively.
They are also saying that this laptime won't actually be made public as it's "5 seconds too slow". So it seems McLaren is trying to beat the 7 minute mark.
The McLaren P1 Did a 07:04 Lap At James May's Favorite Place