According to a letter from the moustachioed thespian, he is getting stopped in the street by strangers telling him he is in the coolest ad they have ever seen.
However, Day goes on to explain that before his hardline credentials fell by the wayside, he used to be a greenie. He refers to his past as an "anti-car bore" and says he was a "radical cyclist" in his youth.
He once even wrote an anti-car play, and not a lot of people can say they have done that. Or seen it, for that matter.
However, the pressures of having a family have clearly battled his principles and won, because Day now drives a rusty old banger, which recently broke down.
He called the RAC and a patrolman arrived. "Aren't you in that Honda ad?" he asked Day, who claimed he blushed with a mixture of pride and shame.
"You want to write to them, mate," the Knight of the Road advised. "See if they'll give you one of them new Civics. You shouldn't be seen driving this heap of crap." Yeah, and according to your ad campaign you should be wearing jet boots, but we'll let that go.
But the patrolman had a point - the widely recognised Day has clearly become a brand ambassador. And as the W&K blog rightly concludes: "I think Honda may just be minded to get him a Civic."
And Honda, if you are still not convinced that Day is living and breathing your brand, get this: "My three-year-old sings 'de possible dream' on a daily basis. The first word she spelt with her fridge magnets was Honda. We are a seriously branded family."
Come on, Honda, you've taken over his life. Give that man a Civic.