Forgive me, but it seems he was driving slowly because there was a huge lorry in front of him...? Also, bit hypocritical seeing as you then proceed to break the speed limit by 7mph.
Incase his insurance providers check in the future and there are negative comments its safe to assume they're false (unless evidence) since he has an internet following.
sorry OP, whilst the undertaking was dangerous, you were complicit in tailgating him to begin with.