Lighting wiring problem - sanity check

[Dave Liquorice]

But you have pulled and waggled the cable which may have caused a problem hidden in the wall. Either snagged on something that has cut through the insualtion (but the "something" would have to be pretty sharp or you have been very rough...). Or mice have nibbled away the insulation and the pulling has created a short.

Seems the wiring in this house is not of a particulary high standard.

[David WE Roberts]

After a good night's sleep in a warm house I have had further thoughts. I think I have had a phantom problem and gone too far seeking a solution.

Firstly, I think that the main issue was that the CH was trying to fire up when I reset the breaker, and the initial surge was too much for the breaker to cope with. After a few tries and holding the switch half way the breaker reset O.K. and has been fine overnight. [JR suggested the problem might be in the breaker.]

Secondly, in looking for a fault (which may not have been there) I was trying too hard. If there is a switch closed anywhere in the circuit (CH, a light, whatever) then there is a route for the current to pass between live and neutral. So a tester will show a connection between L&N. So this isn't a fault, but expected behaviour. I think.....

Now hoping that a sensitive breaker is the explanation for everything.

Thanks for all the suggestions.

Dave R