Lapping Plates using the Whitworth 3 plate method.

My trials and tribulations in creating some lapping plates. Inspired by videos by Tom Lipton over at oxtools So a while back I got inquisitive and started wondering how the first flat surface was made. I mean sure you can compare something to a surface plate, but how was THAT surface plate made and verified to be flat without something else flatter to compare it to? I mean it's like a chicken and an egg problem right? So down the rabbit hole I went and stumbled upon the Whitworth 3 plate method, Tom Lipton and well... here I am. =)