Please!
I’ve had two attempts so far at replacing DP’s loveliest bed sheet. It’s at least 9 years old and was only retired when it ripped. It is silky smooth and on close examination there’s NO fraying! No bobbling, not a fibre out of place, just cool and smooth. It’s defo from M&S and says cotton on the label. Which is a plain label, doesn’t say autograph, but I don’t know how old Autograph is.
I purchased a 400 thread count sateen cotton sheet, and it’s not even close.
The original sheet is defo M&S but the product code no longer exists. Any guesses or recommendations what the magical mystical fibre is before I dive in and spend £75 on the 750 thread that M&S do? I’m sure I’d read that anything over about 400 thread count is just a gimmick! So I wonder if there’s a special weave or type of cotton?
Previous Google rabbit holes saw me purchase some silly number count sheet from an independent that I was so disappointed with I returned it 
Photo attached to compare Holy Grail bedding with 400TC sateen.