It seems to me that Mercian’s quality has always been excellent; the received wisdom at one point was that not all Bob Jacksons are created equal and that some were allegedly “dodgy,” though I have no firsthand knowledge of that.

I can tell you that I love my Mercians, both a 2002 Vincitore custom road fixed gear that I ordered and the 1982 Mercian Colorado that began life as an issued bike for the old Harvest/Mercian/The Spoke team out of Boulder. My riding buddy is equally pleased with his all-road fixed gear based on a King of Mercia and his 80s Vincitore Sports-tourer.

I had a full-blown Rivendell Road Custom that taught me I don’t really want to ride OS tubing for any distance; it was a very stable bike but I never felt speedy on it. My Vincitore built with normal diameter 531C feels quicker, even with 72 degree parallel angles.

How Eroica-ish do you want to go? Classical British bikes for the road were often 72 parallel or 71 seat 73 head angled beasts ....