It's from M&S (I'd guess about 25 years ago 
), supima cotton, plain, long sleeve, fitted (I'd even say tight fitted) with a low round neck.
I love it in the winter and wear it under open shirts, as a base layer under jumpers etc and I'm happy to wear it as a top layer if necessary (if someone's house is warm for example.
I've been looking and looking and I can't find the same.
I don't want a thermal.
It doesn't have to be a low round neck (it could be a v neck or a boat neck but not a crew neck ideally.)
I'd like blue (bright blue) or purple ideally.
Any suggestions very gratefully received.
TIA