Oh dear... I'll not make any more jokes... today, was in a rush to get everything prepared for tomorrow. Got fuel, thought I checked that the fuel-cap was on properly, drove off. When I got home 20km's later, no more original fuel cap. Retraced my steps. Couldn't find it, but most of the roads I drove were alongside water... have a stupid emergency plastic cap now.
Feel really stupid, dumb, and a lot of money poorer. Will retrace steps again later...
If anyone has a spare fuel cap and is turning up tomorrow in Belgium, you can probably sell it to me!
Peter