 This weekend, Commonwealth heads of government meet in the glorious setting of Perth, Western australia, for CHOGM, their biennial get-together with the Queen. But apart from enjoyable Commonwealth holidays on public funds - an old joke made fresh each time by its fundamental truth - concern has penetrated right to the heart of the 61-year-old organisation about what purpose it actually serves.  an internal report, according to early accounts, has been critical of the body's failure to hold member states to account for breaches of democracy and human rights. Concerns are particularly grave over Sri Lanka but stretch to Nigeria via Bangladesh and beyond. Four years ago the summit was held in Uganda, a country where homosexuals are threatened with the death penalty. The summit displaced hundreds of families, cost $130m and left in its wake bitter protests about corruption. The Commonwealth has defenders, like the Foreign Office minister Lord Howell, who insist it remains an important forum for the exercise of soft power. It certainly played an illustrious role in the downfall of apartheid in South africa in the 80s. But if it is to continue to be valuable, it needs commitment, self-belief and a willingness to stand up to states that transgress. In return, it must deliver for its members on the economy and climate change. Otherwise it will look increasingly like an anachronistic self-indulgence - and it will be time at last for the sun to set on the aftermath of empire.