Discussing the weak form of saint (blog, 9 June) reminds me of another word that has a weak form in BrE but not in AmE: sir. As a vocative, it’s sɜː(r) everywhere. But when it precedes a name, in BrE it normally has the weak form sə(r).
So we say sə Humphrey, sə Galahad, Professor sə Howard Fergus.
With a possible linking r, we have sə(r) Alexander Fleming and sə(r) Alan Sugar (star of The Apprentice, recently ennobled and given a cabinet post).
The only circumstance where sir would be strong in this position is if accented for emphasis or contrast. There was a case just today when the Scottish Olympic cycling champion Chris Hoy received a knighthood. Here’s the TV interviewer asking him “How does ˈsɜː Chris sound?”
Note to non-Brits: he’s Sir Chris Hoy or Sir Chris, but never Sir Hoy.