snip snip snip
Right, and you are the one who whinges about 4x4s, or SUVs as you call them? From your description of your outward leg, you travelled 14 miles more than you needed to, and on the return leg a staggering 114 miles more than the route on the motorway and bizarrely still 90 miles more than the distance for going entirely the wrong way around the M25.
You then calculate your mpg by missing out 40 miles of the route and arrive at a figure that is quite frankly unbelieveable for your car.
Even taking it on trust that your MPG was correct, you do realise that you actually used more petrol for this journey than my "monster gas guzzling SUV" would have done, had I driven from Reading to Detling and back?
You don't mention it, but did you not get a Bit Of A Clue when you saw the bridge over the Thames and then drove through a tunnel that you were going the wrong way?
I'd love to have seen the face on the operator at the Dartford crossing.
-- "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety."
-- Benjamin Franklin, 1759