Commonwealth Heads of State and Government meet in London this week. Of the 53 members of the Commonwealth, 19 are African, the largest single group. There are of course historical reasons for this. But it is striking that the two newest members of the organisation (leaving aside welcome re-joiners like The Gambia) are both from Africa: Mozambique, which joined in 1995, and Rwanda in 2009. More are waiting.

So the Commonwealth is beginning to spread beyond the strict Anglosphere, as the Francophonie has expanded its scope to include a growing number of non-French speaking countries. But there is a difference. What holds the Commonwealth together, and what makes it more than a meeting of historically linked partners, is not just The Queen nor the language nor the link to the United Kingdom, but its values and willingness to enforce them. That countries have left – or been forced to leave – and then rejoined is a testament to the reality of those principles and practices.

Africa has been the crucible in which these values have been tested, proving that arguments and negotiations within the community have their place. The rows over South Africa, from its departure in 1961 to its return in 1994, were not comfortable but were a testing ground of the principles on which the Commonwealth should be based. It was Zimbabwe’s unwillingness to respect the (ironically-named) Harare Principles that led to its departure from the Commonwealth in 2003. Zimbabwe’s re-admission, like South Africa’s before, is devoutly to be wished for but cannot be taken for granted. The conditions for membership must be met, and only once free, fair and transparent elections have been held should they be re-admitted.

Many argue that there needs to be more to the Commonwealth than principles and declarations. There have been proposals for a development bank, bigger aid programmes, a privileged trade area, more educational exchanges. It is worth looking at these, where they do not duplicate or overlap or detract from existing multilateral institutions or programmes. But it is more valuable to focus on what the Commonwealth is already providing to its members and build on that.

This means developing the communities of interest and the sharing of best practice between countries in Africa and beyond on the critical issues of democratic practice and the rule of law. Only real accountability will enable governments to tackle corruption, crime and terrorism as well as build development and growth. The meetings between Electoral Commissioners, Chief Justices, Police Chiefs, lawyers and parliamentarians – including from political oppositions – enable exchanges of experience, mutual problem solving and solidarity in adversity which helps build a political culture that is founded on accountability, and government practices that respect it.

This is a precious quality the Commonwealth can bring to all its members, large and small, in Africa and beyond. It is an issue on which the small can teach the large as much as vice versa, and which makes the Commonwealth something to treasure. Let us hope CHOGM reaffirms that and pushes it forward.