[classicgreendog]

Thanks Guys,

I have fitted a new thermostat, and I fear you could be right, but nothing
is obvious. The car has stood for 3 years or more and it has blown before I bought the car. The underside of the bonnet and the top of the engine show signs of heat by way of crackled paint etc.,
The top of the radiator does get hot.

I took the car for a 15 mile run this morning and it behaved perfectly.
The temp gauge held perfectly steady at 80 degrees in and out of traffic.

regards,
Mike