Surgeons are always addressed as Mr or Miss in the United Kingdom and the Republic of Ireland.
The tradition arose before 1800 when physicians were by definition doctors who possessed a university medical degree (an MD). Surgeons seldom had any formal qualifications. Physicians were also members of the Royal College of Physicians founded in 1518.
The growth of voluntary hospitals in the 18th century brought high status to surgeons.
After the founding of the Royal College of Surgeons of London in 1800, surgeons had a formal qualification (the MRCS)
Surgeons became so proud to be distinguished from physicians that the title of Mr became a ‘badge of honour’. Gynaecologists also refer to themselves as Mr or Miss.