Set off at 10, got rained on a fair bit so stopped after 80 miles at a bp garage outside wrexham. I thought I might as well fill up, so I went to pump, selected the green/blue one which said bp ultimate. Put in 9 litres. Oh.
It's bp ultimate diesel. Thanks BP that was really obvious. Diesel is black, petrol is green and bp ultimate is green with a blue bit below it saying diesel.
So here's how you get out of such a fix. Don't call the AA. They won't recover you even with full membership becuase its 'self inflicted'. b8stard. They will however come out if you lock the keys in the car - apparently this is not self inflicted. Tell me the difference?
They do however helpfully offer to come and drain it for a bargain £212, providing you can be bothered to wait 4 hours - the normal speed of service doesn't apply for this instance.
So - we scratched our heads and decided to do it ourselves. Found a building site nearby, nicked a bit of hosepipe and a bin. Siphoned out 18 litres of foul smelling yellow stuff

Easy eh?
Epilogue: the AA man turned up just as we put our helmets on, ready to go. He had been sent by the call centre to explain in person why they wouldn't be able to help. Now that's service.
Oh - the rest of the day was a ball - Bala round trip

