Coming home from the Silverstone Classic back up to Leeds this summer it threw it down all the way and as long as I kept above 40-50mph I stayed dry. In fact I got wetter driving the last 2 miles home from the motorway standing at traffic lights and doing 20-30mph than the previous 150 odd.
Attire:
Half toneau, over trousers, Barbour jacket, gloves and full face helmet. = warm and dry.