Was stuck up in traffic, just like me going M4 westbound yesterday afternoon about 1:30-2:00pm-ish.
Looked pretty quick.
Tried to catch up and get in convoy but too many Sunday drivers in the way and couldn't start undertaking now

Suspect you may have noticed the utter **** in the blue Vauxhall Astra undertaking everyone and then cutting in behind you a few times - nearly wiped out a guy in a people carrier - he did NOT look happy.