Common Law offence of Breach of the Peace...OK...
Well first we have all assumed it is a UK registered Aircraft, otherwise B of P cannot have happened (the full title being breach of the Queens Peace).
Jaydoubleyou...You say that he was committing a B of P which could endanger the safety of the aircraft...Where's your evidence? You don't have any you were not there. Secondly Endangering the safety of the aircraft is a specific offence quite seperate from B of P. I can see no evidnce that supports your assumption. It's made crystal clear on UK aircraft that smoking is not permitted. This guy was not smoking. Yes the CC have the duty to establish that, but after that point, wheter you like it or not, thats the end of the matter. In any case as the original post says the toy was 'put out'. Any B of P would at that point cease (had there been one in the first place) What could or could not have happened is irrelevent as nothing did happen.
If the mans actions amounted to Endangering the safety of the aircraft, then why were the local Police not called on arrival? That offence is serious and carries a prison sentence, it's also by International convention capable of being dealt with in another country than the country of registration of the aircraft (B of P isn't)
Given that any B of P ended at the point of the toy or whatever you want to call it was put away, and there is no evidence whatso ever of endangering the safety of the aircraft, then for what reason was he detained until the captain had spoken to him? None...there is no such power. The Human rights act forbids the detention of anyone unless by means of thier lawful arrest, there is no lawful arrest, as there is no offence. That leads the crew open to procceddings.