Even if Mugabe decided he had had enough, he would have to face the fact that he has become a hostage of his own system. Over the years, he has cleverly woven a web of patronage. Party officials, senior military and police, high court judges and even bishops have been kept on side with handouts of farms and access to perks such as cheap fuel and an official exchange rate that enables them to buy foreign currency for a hundredth of the market rate.

This has created a mafia of several thousand people, many of whom have blood on their hands. Should any contemplate switching sides, meticulous records kept on file in a special archive in the Reserve Bank could be used against them.

Key figures who see their survival at stake include Constantine Chiwenga, the army chief, Augustine Chihuri, the police commissioner, Henry Muchena, an air vice-marshal, a number of former military commanders, Gideon Gono, the powerful governor of the Reserve Bank, and long-time politburo members such as Didymus Mutasa.

Although Tsvangirai says he has promised Mugabe “an honourable exit”, he cannot give guarantees to all these others. “No matter what Tsvangirai says about guaranteeing President Mugabe’s safety, we cannot trust the man,” said a member of Zanu-PF. “If one day he gets a call from Gordon Brown or George Bush and is told to arrest Mugabe, do you think he won’t do that?”

The military hierarchy is particularly worried. A leaked memo reported Muchena, the air vice-marshal, as stating that Zanu-PF “did not fight a liberation war to have Zimbabweans vote incorrectly. The military has now taken over the organisation of the campaign and five senior military officers have been assigned to each constituency to ensure that in the next round the people vote correctly”.

For his part, Tsvangirai has resisted pressure from younger members of his party to call a mass uprising. He told me last month: “If I’d put people on the streets last time, they would have been mauled to pieces. I don’t want to be responsible for this.”