BOAC,
Yes, I agree although I wonder if it would come down to who had the better barrister pleading force majeur.
It would be interesting to have a (without prejudice) opinion from Flying Lawyer.
It is, of course, a criminal offence to fail to comply with the ANO:
CAP 393 AIR NAVIGATION: THE ORDER AND THE REGULATIONS
AMENDMENT 3/2008
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.
Acting in a disruptive manner
78 No person shall while in an aircraft:
(a) use any threatening, abusive or insulting words towards a member of the crew of the aircraft;
(b) behave in a threatening, abusive, insulting or disorderly manner towards a
member of the crew of the aircraft; or
(c) intentionally interfere with the performance by a member of the crew of the aircraft of his duties.
p.s. I cannot imagine not having my seatbelt secured whilst seated even if the Fasten sign is not illuminated.