One possible lead is the loss of an Iberia Caravelle at Blackdown Ridge, Surrey, UK in the late 60s due to possible misinterpretation of a 3 pointer altimeter. It would have been late October/early November- I was at a fireworks display on a dirty night some miles SW of where it crashed and it we heard it come low overhead. One of those on board killed was the lovely TV comedy actress June Thorburn (
http://www.imdb.com/name/nm0861185/)
and I see that site says the date was 4 Nov 1967.