Re: [tz] Europe/London Sat Oct 26 23:00:00 1968 UT

Looks like isdst should be 1 on

Europe/London Sat Oct 26 23:00:00 1968

The convention is that if clocks are the same all year round and if this appears to be intended to be permanent, the isdst flag is zero even if the enabling legislation uses phrases like "daylight" or "summer". An example of that is the Turks & Caicos change in November. My vague impression is that that three-year period you're talking about was intended to be permanent. I haven't researched this, though.