Re plugs traditionally spark plugs were manufactured with glazed ceramic central electrodes. This has been cost sut out of recent production with a few decades of lean burn otto cycle engines. This is a problem if plugs get wet from flooding on cold start, which is an occupational hazard with our cars (especially 1600s). It kills the plug and it is never the same again. Regular plug changes mitigates against this....
As it happens, I believe I have had just this experience starting up my Aurelia B20 S1 for the first time this year. It refused to fire on all 6 but having changed the relevant plugs ( which were almost new) for other barely used plugs the problem was solved. I thought I had a couple of faulty NGK plugs but I realise now that they had almost certainly been wetted from flooding using the choke.
Chris