Velocette LE ["Little Engine" ie 149 or 200cc] also nicked named a Noddy Bike. Built between 1948 and 1971.
Water-cooled 4-stroke horizontally opposed twin, ran very quietly which gave them another nickname "whispering death" ...

This is FLB 26C, so registered in 1965
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en.wikipedia.org/wiki/Velocette_LE