I'd guess a lot of it technology based: 1 - BBS trading evolution/rise of ATS 2 - Internet/.com (bubble and collapse) 3 - sophisticated computer modeling for structured products 4 - explosion of financial derivatives market 5 - wasn't around for NMS but bet tech is what made it feasible

It’s really funny because the OPR is the most Euro-coded regulation ever. Meanwhile the EU best execution rule is a really Americanesque approach Weird moment on time