Enough. While the world stands by, the people of Zimbabwe are dying. The mismanagement of Zimbabwe by its first and only ruler since independence, Robert Mugabe, defies bromides about the affront to civilised standards; but they are true none the less. The Elders group of international statesmen declared yesterday that Mr Mugabe had “not demonstrated the ability to lead the country out of its current crisis”. Raila Odinga, Kenya's Prime Minister, called for the African Union to authorise sending troops into Zimbabwe.

It is a crucial moment for Zimbabwe, for Africa and for the international order. Self-determination and sovereignty are cornerstones of the Wilsonian system of independent nation-states. But in its state of misrule, Mr Mugabe's regime has forfeited legitimacy. Proposals for African-led military intervention are right and urgent. The UK Government should join those calls.

Blessed with fertile land and mineral deposits, Zimbabwe was once among the most prosperous of sub-Saharan African nations. It is now a place of penury, disease and oppression. The currency is worthless and the people are starving. The collapse of the sanitation system has sparked an epidemic of cholera that threatens to spill over to neighbouring states. While the social condition of Zimbabwe is now extreme, Mr Mugabe's brutality is not a recent development. It emerged at an early stage of the country's post-colonial history, with a murderous campaign against the ruling party's rivals in Matabeleland in the 1980s. Mr Mugabe then cemented his hold on power by violence, corruption, patronage, ballot-rigging and intimidation of his political opponents. His regime has robbed Zimbabweans of their rights, their livelihoods, their possibilities for a decent life - and, by the scores of thousands, their lives.

There is not a direct precedent, but there is a disturbing echo, in the Rwandan crisis 14 years ago. Western diplomats then invested too much faith in the notion that the state they were dealing with was an essential party to political settlement. In fact, Rwandan officials were in some cases covertly planning acts of horrific brutality.

Times Archive, 1983: And now the real Mugabe stands up

His elegance of speech, and gentleness of manner, have deceived many in the West

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No Western government has illusions about the character of Mr Mugabe's regime. But there is a presumption that even a shameless autocracy and kleptocracy has a claim to be treated as a legitimate state actor unless it directly threatens another state. By the depredations perpetrated against Zimbabwe - its polity, its society, its economy and above all its people - Mr Mugabe is now head of an outlaw regime. More than 20 years ago, Bernard Kouchner, the French Foreign Minister, identified a duty to intervene when human rights were abrogated by a literalist stress on state sovereignty. If his argument applies anywhere, it applies to Zimbabwe.

The UK Government will note that good men such as Archbishop Desmond Tutu and Archbishop John Sentamu of York are calling for the forcible overthrow of Mr Mugabe. Out of a bond of humanity, the Government should join that call, and make clear that it supports the authorisation and use of force by troops of the members of the African Union.

It is urgent for Zimbabwe's neighbours that the regime now be toppled, lest this rogue state implode and become a source of instability and suffering throughout the region. British troops should not be at the forefront of an intervention; but they should be made available if there is a request from the African Union. The aim of an intervention must be to excise Mr Mugabe's regime, install an interim government, set in train the process of fresh elections, distribute food and ameliorate the appalling state of public health. It is the continuation of diplomacy and humanitarian assistance by other means.