The same surgeon is Mr in London and Dr in Dubai.
In the UK, physicians once earned a university doctorate, and the title came with it. Surgeons trained as apprentices and sat an exam for a diploma, so they stayed Mr. Today every surgeon goes to medical school first, but the custom stayed. As the Royal College of Surgeons puts it, a surgeon starts as Mr, becomes Dr, then goes back to Mr.
A patient in Dubai looking up a London consultant knows none of this. She sees Mr where she expected Dr, and wonders whether he is a doctor at all.
I used to think British surgeons were just being humble. Now, before I write the first line of a profile, I check what the surgeon goes by and who will be reading it.