Ronnie does wear an IWC fairly regularly. It's an IWC Mark XVIII Edition (Tribute to Mark XI).
I'm watching the Lisowsky/Allen game just now as I recorded it earlier this evening.
He usually wears a Rolex GMT or Patek but this particular watch is unusual. It looked like a European Company Watch (E.C.W.) Panhard or something very similar when I first saw it. I spotted the Panhard styled case with screwed lugs. E.C.W. don't normally supply bracelets. That (and the fact that it has an octagonal bezel) gives it away. It must be an AP.