However, like it or not, that sketch is the only frame of reference most people have for who Preview was. You have to talk about it. I'm sorry to have to tell you this, but for the majority of people, that appearance on the Morcambe and Wise Show is the defining moment of Preview's career. Probably more people watched him on that show on its first airing than have ever seen him conduct an orchestra.
I'm sorry Jeremy but I can't agree with you and you comment is amazingly UK-centric and parochial.
Andre Previn was a global star of the music world. While most of his career was spent in the USA, he held major positions on 3 continents and was a star in every continent. M&W, by contrast never made it beyond the UK. Indeed Previn had won 4 Oscars by the time M&W were making their failed attempt to break America in the mid 60s.
So it might be true that in the UK 'that sketch is the only frame of reference most people have for who Preview was'.
But in Germany, the country of his brith - nope
In the US, the country of his residence and most of his work in Hollywood and various orchestras - nope
In Norway where he was director of the Oslo Philharmonic - nope
In Japan where he was director of the NHK Symphony Orchestra - nope
etc, etc
Indeed I suspect the majority of people in those countries will never have heard of M&W, never seen that sketch and if they had the point of reference (the person they knew) would be Previn introducing them to the unknowns of M&W.