My original Lambert that I bought back in the '70s (a brazed Viscount Aerospace with sealed bearing press-fit B/B) and used for road racing, TTs and later 'Cross - including 2 x Three Peaks complete with "Death Fork" was definitely a 27.2 post, because I had to replace the faux Campag piece of crap that came with the bike and did so with a standard campagnolo 2 bolt 'post.
The later Viscount I have now - a brazed jobby with threaded B/B is a 26.8...
Ian Briggs
Luton, Bedfordshire, UK