Moments after formally agreeing to enter talks on a power-sharing deal, President Mugabe cautioned against outside interference. “As we embark on the programme of negotiating the way forward ... we shall be doing this as Zimbabweans ... with South Africa,” he declared.

Less than 24 hours after Monday's signing ceremony, the European Union - showing an exquisite sense of timing - agreed to broaden sanctions against Zimbabwe. EU foreign ministers said that it was important to keep up the pressure. Bernard Kouchner, the French Foreign Minister, said: “Sanctions have played a role. We have to keep up that role.”

He could not be more wrong. What the West, particularly Britain and the US, fails to understand is that it is precisely that pressure which has allowed Mr Mugabe to defy predictions and remain at the helm of the country way beyond his sell-by date.

Sanctions - including travel bans on regime officials and the freezing of their overseas assets - have been an unmitigated failure. Most of the elite have been able to ignore them; Mr Mugabe is still in power and the country is in ruins.

For years it has been a perennial refrain from the ruling Zanu (PF) party that Morgan Tsvangirai is little more than a puppet of former imperialists. Many people believe, with commodity prices at record highs, that Britain wants to get its hands back on Zimbabwe's mineral riches before China takes them. Mr Mugabe has exploited that unease adeptly for years. The West has always proved a willing helper: talking tough, threatening action and making clear its obvious distaste for any deal other than the former “freedom fighter's” departure. By so doing it has strengthened Mr Mugabe and undermined those regional voices wanting him to step down.

The West's failure to heed the lesson from past errors and adopt a different strategy lies at the heart of repeated failures of its diplomacy since the current Zimbabwean crisis began three months ago. It led directly to humiliation in the Security Council ten days ago when Russia and China vetoed a resolution imposing tough sanctions on Harare.

That vote also reflected the reality of shifting power alliances on the continent. Britain, in particular, has been slow to appreciate how little it can influence events in its former colony unless it has the backing of neighbouring states.

President Mbeki, who has been ridiculed for his “quiet diplomacy” on Zimbabwe, made it clear that he believed a UN vote on sanctions would make it even more difficult to get talks started on a government of national unity. Consequently he lobbied hard and succeeded in obtaining the veto. The vote also demonstrated how much Africa now matters to Russia and China, both of which have built up huge commercial interests on the continent in recent years.

Even Zimbabwe's most critical neighbours, Zambia and Botswana, favoured the South African approach to the frantic “Mugabe must go - now” tub- thumping of London and its European allies. Commentators argue that few people in the region believe Mr Tsvangirai and his MDC party hold the answer to the country's problems. More importantly, they know that Mr Mugabe's henchmen in the security services will only let him retire as a part of a broader negotiated settlement.

It is far too early for Mr Mbeki's approach to be vindicated, but a look at the memorandum of understanding signed by Mr Mugabe and Mr Tsvangirai shows how far he may have come.

The agenda for talks includes a new constitution, the promotion of equality, national healing and cohesion and unity. At the signing ceremony, the Opposition was upbeat while Mr Mugabe was resigned. “Everyone accepts Mugabe will not be there when the talks are over ... well, that is unless the EU and Gordon Brown keep trying to help speed things along,” said one exasperated South African diplomatic source.

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