According to the House of Lords' Decision in Bolitho V

According to the House of Lords' decision in Bolitho v City and Hackney Health Authority, a professional will not be in breach of their duty of care if they…

A) have acted as a reasonable person would have done.
B) have acted in accordance with a practice accepted as proper by a responsible body of people skilled in that particular area, even if that practice was logically insupportable.
C) have acted in accordance with a practice accepted as proper by a responsible body of people skilled in that particular area and the practice is logically supportable.
D) have acted to the best of their ability.