Don't forget the "get out of jail" card (for those who operate under JAR-OPS 1) - JAR-OPS 1.085(g)
(g) The commander or the pilot to whom
conduct of the flight has been delegated shall, in an
emergency situation that requires immediate decision
and action, take any action he considers necessary
under the circumstances. In such cases he may deviate
from rules, operational procedures and methods in the
interest of safety
and in the UK, ANO article 77 -
Authority of commander of an aircraft
77 Every person in an aircraft shall obey all lawful commands which the commander of that aircraft may give for the purpose of securing the safety of the aircraft and of persons or property carried therein, or the safety, efficiency or regularity of air navigation.
In extremis, a captain can do whatever he considers best and you'd better obey.
