Could he have done it anyway? and gotten removed I guess
Difficult to say for sure, as the UK doesn’t have a written constitution.
However, with military intervention in Syria being deeply unpopular in the UK, it would’ve been a big risk, with an election likely 12-18 months away there. In a way this result suits Cameron - he doesn’t have to get involved in Syria, but he can hold his hands up to Obama and say ‘I did my best, sorry...’