The Queen arrives in Uganda on Wednesday to begin a two-day state visit to an African country that in many ways has been a beacon to the continent in showing how to overcome dictatorship and economic collapse. For although Yoweri Museveni, the President, has shown autocratic tendencies and a recent reluctance to observe constitutional term limits, he has, for 20 years, nursed Uganda back from the ravages of Idi Amin, confronted the scourge of Aids and given a younger generation stability and modest prosperity. Two days later, the Queen will preside over the opening of the biennial Commonwealth Heads of Government Meeting that will itself have to take far-reaching decisions on repression in some of its members, misrule in others and the enforcement in all 53 members of the principles of good government and democracy on which this unique grouping is officially based.

The most divisive issue will be Pakistan. The Commonwealth has long taken a strong stance against military rule. It condemned putsches in The Gambia and Sierra Leone, ultimately forcing those who seized power to hold elections. It struggled for more than a decade with military dictatorship in Nigeria, setting up a standing Commonwealth Ministerial Action Group (CMAG) to step up the pressure on the corrupt and intransigent junta. It suspended Fiji three times after coups, expelled and readmitted Pakistan from membership once before, suspended it again in 1999 and was persuaded only with difficulty to readmit the country in 2004 to give General Pervez Musharraf time to restore democracy.

His declaration of a state of emergency this month, however, has been a step too far. An emergency meeting of CMAG last week gave him a ten-day ultimatum to restore democracy or face expulsion. It is a step that, together with the blunt warning at the weekend by John Negroponte, the US Assistant Secretary of State, will carry weight with the embattled general. Pakistan attaches considerable importance to the political, cultural, educational and sporting links that come with Commonwealth membership. President Musharraf wants desperately to win respect and understanding for his actions. CMAG, comprising foreign ministers from all parts of the Commonwealth, cannot be portrayed as another Western body preaching to the Muslim world; it represents a cross-boundary consensus on democracy that has proved surprisingly effective where other bodies has achieved little.

It has been fashionable in Britain to write off the Commonwealth as an organisation that is inherently antiBritish or institutionally ineffective. Both claims have been true in the past, but the Commonwealth crosses most political, regional and wealth groupings. Many of its members, including the present host Uganda and its neighbour Kenya, have difficulty living up to declarations on good government. And the summits inevitably produce more talk than substance.

But the Commonwealth has a unique behind-the-scenes influence, based on shared history, a universal language and a common legal and educational heritage. The mix of great cultural diversity and shared values is unusual and useful. Gordon Brown may find, in Kampala, more agreement on principles than is often the case. The frustratingly complex problems will not be solved immediately, but members should understand that if they want a greater stake in the Commonwealth’s leadership then they must take the lead.