I’m just about old enough to remember when smoked salmon was a rare treat. Then, around 1986 or 1987, suddenly it was everywhere. There were smoked salmon sandwiches at M&S, it was stuffed into lurid-looking canapés with cream cheese, and Christmas became a riot of salty fish. For me, smoked salmon is as emblematic of the 1980s as red Porsches, huge mobile phones and the Pet Shop Boys.