When I was in 6th form (1980!) had a cardigan from Next - when Next were only a few years old and were a good quality, slightly above average shop for thinking women's workwear. It wasn't that amazing, but it worked really well for me.
It was lambswool. Boyfriend style (except it wasn't called that then, it was just a v neck cardy then). Not too thick for summer, not too thin for winter. It was just the right shade of cornflower blue to make my eyes pop, and made me just look amazing. It was long enough to reach the top of my trousers (I have a long back, this is my holy grail in tops). Slightly oversize. Slightly oversize, but not chunky, pearl buttons. I wore it to pieces, literally.
I have tried to replace it so many times over the years. Nothing is ever quite right. Woolovers did a good blue a few years ago, but the cardigan was too short and the buttons too fiddly. Two or three other "cornflower" or "bluebell" pieces have proven to actually be drab, smokey, RAF blue. It needs to be lambswool. I'm can't wear synthetics without stinking! I'm too rough for anything delicate like merino or cashmere. (TBH, I'd settle for Shetland wool if everything else was perfect).
I do miss that cardigan.