So we sat there for a bit cooling off, and then I restarted the engine, which made a very unhappy noise, but did kick into action. We travelled perhaps 200 yards before the temperature gauge got near the red, and we had to stop and have another nice rest for a while.
We travelled onward for some way in this manner. Fortunately most of it was downhill, so Helga could just roll. I got as far as a local garage, where the guy had a quick look, and thought probably the water pump had gone - but there was a side bet on it being the head gasket as well. And he was about to go off on holiday, and could not fix it.
I parked Helga around the corner, removed the dogs, and walked home. A non-functioning car is a nuisance, but a non-functioning car full of large impatient dogs is a real problem, because car retrieval services won't take dogs except by towing them inside the car. Then once you have got to somewhere that can fix the car, if they can't fix it there and then, you and your dogs are stuck, because even if they have a courtesy car or you try to rent a vehicle, it will certainly have a 'no dogs' clause**. I suppose I could have got a taxi* eventually but taxis in rural areas even nowadays are rather slow to arrive. Walking home seemed easiest. So I did that.
Then I phoned around to try to find a garage that was downhill of where I had parked that was prepared to try to squeeze poor Helga in for an urgent appointment. RESULT ! I found one. So then I had to walk back to Helga, and roll her down the hill to Garage The Second. And then walk home again. Cornwall really does have more than enough steep hills. By the time I got home I had done more than enough walking for the day.
But! The head gasket had not gone, and my careful stopping and rolling and watching the temperature gauge had worked: the overheating problem had not cooked anything important, and the garage were able to fit a new water pump. Helga, with 154,127 miles on her clock, lives to roll another day.
* There is at least one local taxi that takes dogs, because the other day Brythen, alarmed by an explosion, got out of the garden and went gallumphing off before I could stop him (he had made a hole in the hedge, which I have since fixed). When I went charging off through the village after him, I found him being chauffered back in style by Kit Hill Cars, looking very pleased with himself.
** although, of course, if you hoover the courtesy car really, really well afterwards, they probably can't tell. Or at least, nobody ever got back to me to complain. But I hate hoovering.