What do you say to a man widely blamed for beating you, stealing your job and trying to have you thrown out of a 10th-floor window? Morgan Tsvangirai, prime minister of Zimbabwe, insists that he is now able to joke with his long-time opponent, President Robert Mugabe.

"Over a long period of time you start to develop some chemistry," he says, leaning forward in a black armchair in his ministerial office. "That's where you can't just go in and talk about business, you actually have to talk about personal issues. Sometimes it's helpful to unlock the barriers that may exist between people."

The democrat and the dictator are six months into southern Africa's most curious marriage of convenience. Their power-sharing agreement followed a bitterly contested election that robbed Tsvangirai of victory and left scores of his supporters dead. Their two parties continue to fight, but Tsvangirai describes the odd couple's meetings as "cordial … not acrimonious".

He explains: "There are certainly many areas where we differ, but we agree to differ. We communicate, we talk, we discuss, we don't believe that there's anything insurmountable to discuss … I'm very free. I've decided that I will not keep anything to myself. I will express it and express it forcefully if it affects my own constituency, my own party and the general thrust of the inclusive government."

Recently, for example, Mugabe made a populist speech to assert Zimbabwe's disdain for western help, in direct contravention of the policy agreed with Tsvangirai. The prime minister used humour to defuse the tension by remarking: "Well, your statement was quite predictable." Mugabe, apparently, laughed it off.

Tsvangirai has proved doubters wrong simply by still being here and holding together the fragile compromise. The unity government has rescued the economy from the brink and slowly put schools and hospitals back in some semblance of working order, though the headaches that remain are legion.

Plenty of sceptics believe the president, who retains the "hard power" over the army, police and law courts, is bending the prime minister to his will. Tsvangirai insists, however, that the man who has ruled Zimbabwe with an iron fist for 29 years is no longer the main obstacle to democracy.

"This is a perpetual suspicion of Mugabe," he says. "It's a template. People can't believe that Mugabe has any capacity to change. It's an inherent mistrust and it's nothing to do with what we are trying to build."

So does Mugabe, even at 85, have the capacity to change? "I have no doubt he himself is committed to see this through. I have no doubt that perhaps there could be people in his own party or other elements who have reservations about it, but so far I think we are moving to achieve those incremental gains."

He continues: "You must understand Mugabe's political character has always been a character of denial, shifting blame for his own shortcomings. But it's always good to have a legacy, and I'm sure that for him, it is the positive aspects of his life that he wants to take, not to be reminded about the negative aspects."

Last year, it is estimated that about 200 of Tsvangirai's supporters in the Movement for Democratic Change (MDC) were murdered in violence perpetrated in the name of Mugabe's Zanu-PF. And more than 200 people were massacred when troops seized control of diamond fields in the eastern Marange district. Yet Mugabe apparently tries to laugh off his global infamy.

"He jokes about it. He says, 'People say I'm a tyrant.' So what do you think of yourself? He says, 'I'm not a tyrant.' … We don't ignore what has happened. Sometimes those things are facts on the ground which have characterised him."

Tsvangirai himself was once almost hurled from a 10th-floor window by men thought to be from Zimbabwe's secret service. He has faced three more attempts on his life and been repeatedly beaten and arrested. It is widely considered that Mugabe stole the elections from him in 2002 and again in 2008.

How, then, does the 57-year-old bring himself to now sup with the devil? He replies: "What is reconciliation without that? Reconciliation is a measure of tolerance across the very serious political divide that has existed in this country. How can we stand up as leaders and call for national unity when between us we don't relate to each other?"

Tsvangirai admits that Zanu-PF's influence over the judiciary remains problematic but dismisses fears that continuing arrests of MDC MPs will threaten the party's parliamentary majority, saying that he will simply put up more MPs in their place. He is equally sanguine about the threat of assassination, despite his finance minister, Tendai Biti, having received a 9mm bullet in the post last month.

"Those threats I don't think will go overnight. There are people who feel threatened by the very existence of the inclusive government: it threatens their patronage, it threatens their benefactors, so naturally they react."

Conspiracy theories continue to swirl around the car crash, less than a month after he became prime minister, in which Tsvangirai was hurt and his wife, Susan, was killed. He insists it was an accident.

Tsvangirai's conciliatory attitude has led to criticism, not least from within his own ranks, that he has conceded too much ground to Mugabe, sacrificing change for the facade of unity. Sceptics prophesy that, come the next election, violence will flare up again and the power-sharing agreement will be worthless. Tsvangirai vehemently rejects the charge. "I'm not bending over backwards. This is a shared compromise. It has never been meant to be winner takes all … It's not a perfect marriage. It's a marriage that is meant to ensure that this country moves forward and so, yes, frustrations will be there.

"But let's not miss the goal … We will keep our eye on the ball until such time as we are going to have an election which is free and fair."

Troubled times

1952 Born in Gutu, eldest son of a bricklayer.

1978 Marries his wife, Susan. They have six children.

1988 Becomes secretary-general of the Zimbabwe Congress of Trade Unions.

1999 Helps form the Movement for Democratic Change with support from students, trade unionists and white commercial farmers.

2000 Charged with treason; charge later dismissed.

2002 Loses presidential election.

2004 Acquitted of treason after 18-month trial.

2007 Survives brutal attack by police.

2008 Captures the most votes in the presidential election but Mugabe refuses to relinquish power.

2009 Sworn in as prime minister in unity government. Loses his wife and grandson in separate accidents.