The Individual
Litebulbs,
If somone was dismissed for "forgetting" or "choosing not to", and then they went to an employment tribunal, it would be the panel that finally decided whether it was a reasonable instruction or not. Without taking a management or Daily Mail stance, in this case, BASSA Admin would seem to be believe that it is not reasonable (in Employment law context), whereas Unite's position would seem to be that it is reasonable. (note, they make no suggestion that closing the blinds should be subject to a grievance procedure, failure to agree, etc.).
Additionally, an ET would look at each case on its merits (and presumably BA's own internal processes would do the same for the dismissal to be fair - if they didn't, it would be automatically un-fair, irrespective of reasonableness). For eg, was there a pattern of not doing it, did the individual state that they deliberately didn't do it, were there any extenuating cirumstances, etc. It is exactly the same with any disciplinary issue investigation. So there is no simple answer to the question.
FWIW, I can't see an argument that because it has been custom and practise not to close blinds, that therefore an instruction to do so is unreasonable is going to get anywhere.
nb what has a discussion about the very specific area of Illegal Deduction of Wages (which carries its own very particular set of case law and legislation) got to do with closing blinds ?