Horse 1241 - The Point of the Commonwealth

With the Commonwealth Heads of Government Meeting being somewhat spoiled by the industrial actions of Qantas and the Unions, I thought I'd ask the wider question of "Just what is the Point of the Commonwealth anyway?"
In the 21st Century, the Commonwealth of Nations appears to be little more than an historical accident, it would appear that the only common thing linking the Commonwealth is the freak of history of all being ruled by one small dinky island at some point. Is there more to it than that? Should there be?

If I take a potted look through history to find the longest continuously sitting parliaments, I find in order:
The Isle of Man which has been sitting since 930, Newfoundland 1855, New South Wales since 1856, Victoria 1856, Tasmania 1856, South Australia 1857 and Queensland 1859.
I do realise of course that Britain herself has had its Parliament in its current form since 1701 with admissions and modifications but it didn't sit during World War II, and the United States and every State within the Union which I've found, either ceased sitting during the Civil War from 1861-1865 or held erratic sittings and a situation of martial law existed.
Given that the children of Westminster ("the Mother of all Parliaments") appear to be the most stable forms of government in the world, surely there is a common underlying reason for this. What is it exactly? I think that it's Common Law and the Law of Equity.

Common Law which is also the law of precedence or case law, assumes that the decisions of judges, courts and similar tribunals are binding on future decisions. Common Law says that it is unfair to make differing decisions if the facts in a particular case are similar to something which has gone before. The law itself assumes and tries in spirit to be consistent and more important just. As far as Common Law is concerned in all countries which have an English Common Law tradition, Common Law begins on 6 July 1189 which is the end of "Time Immemorial"

The point of Common Law as it applies to the Commonwealth and why it appears to be such a stable basis from which to run a legal system, is that it does not change. There is something to be said about the benefits of a Westminster style legislature, but given that the UK doesn't elect the Upper House, Queensland and New Zealand don't even have an Upper House, and Ireland and India (the latter which somehow amazingly manages to hold together 21 major languages and 212 major tribal groups), I don't think that it is the defining feature which causes stability within Commonwealth countries.

Britain's Secretary of State for Foreign and Commonwealth Affairs, William Hague in a speech to CHOGM said that:
"The case for reinvigorating the Commonwealth is abundantly clear and Britain whole-heartedly supports the recommendations of the Eminent Persons Group.
In particular, we welcome their focus on promoting the values of the Commonwealth."

It's curious, but the thing which most closely binds the Commonwealth isn't the style of parliament (even though I like Westminster parliaments) and it isn't even the monarchy. I think that it's the tradition of Common Law, and the stability which flows from that.