I had something similar on my car outside my house, nice quiet residential street in a nice end of Cheltenham.... turns out it was a neighbour 2 doors down, caught her picking it up after I purposefully put it on the curb. I confronted her and she launched into a massive rant about how I was killing her kids with C02 and if I hit one I was 3 million times more likely to kill them.
She was less than impressed when told her to keep the little bastards inside!
After that she looked at her piece of paper and informed me that my horrible 4X4 did 15 mpg. WRONG!! So I showed her my trip computer, I am presently getting about 28-32mpg, it was on 30.2mpg as I am on the motorway for 99.9% of my trip - she went quiet.
Then I noticed than in her driveway she has an X reg Audi A6 avant 2.8 petrol (her husbands). I informed her that her car does significantly less mpg than my RR and that she was killing my daugher.
One speechless, uninformed and more than a little annoying bandwagon jumper!
How long do you reckon until her A6 get changed for a Toyota Prius!?!?