For Anyone Interested

[KARL]

Around two months ago I was grappling with a particular car problem.
https://www.theanswerbank.co.uk/Motoring/Question1678064.html

Eventually I got the car going, basically without doing anything except stubbornly trying to start the thing and ultimately it sort of gave in and ran again. However, it remained less than perfect and it was not long until it would refuse to idle, i.e. run without a foot resting on the accelerator (could be an absolute pain at non-right of way junctions). For a variety of reasons I could not see to adjusting the carburettor setting until a few days ago. It transpired the entire carburettor/air filter assembly was insecure, it could be made to wobble. The carburettor mounting flange was broken and a variable gap was allowing air to bypass the carburettor channel and get into the intake. The flange has been replaced and so far the car runs perfectly.

I cannot say whether this contributed to the earlier mysterious problem but I very much doubt that it was the main cause - I don't think the manifestation was there at that time, at least nothing like as great. Still, I offer the story as a sort of update on the original post.

[gulliver1]

Glad, you are sorted Karl.

[douglas9401]

Good news Karl.

Flange is one of my favourite words. :-)

[Hopkirk]

Thanks for letting us know.

[bhg481]

Thanks for letting us know, KARL.

I haven't had a car with a carburettor for about 30 years now, so it just wasn't in my world model. As you say, it still doesn't explain the flat-battery syndrome - just one of life's mysteries.
It reminds me of a time about 40 years ago when a friend had a Wolseley 18/85 which decided it would stop the engine whenever he turned the steering wheel in either direction. The car would start again with no problem and idle nicely. We solved the problem by me standing on the front bumper with the bonnet open and him driving the car slowly. As he turned the steering the power-steering hoses flexed with the load and lifted the LT wire off the coil, thus killing the spark. As soon as the engine stopped the wire dropped back into position and the car would run.