Meeting is Unnecessary - meetings and resolutions:

The purpose of holding general meetings with all the formality which this entails is to give to each member the opportunity of voting (in person or by proxy) on the resolutions before the meeting.  If the meeting is not properly convened and held its purported decisions are not binding on any member who disagrees with and challenges them. His right to do so exists whether he was absent from the meeting or attended it but was in the minority.  But this is a protection given to a dissenting member.  If every member in fact agrees it would be pointless and wrong to allow any non-member to dispute the validity of the unanimous decision because unanimity was achieved in some informal way.

Accordingly a unanimous decision of the members is treated as a substitute for a formal decision in general meeting properly convened and held and is equally binding.