Each day, in his office above a printing shop in a forgettable suburb of Cape Town, he begins by quietly petitioning the Almighty on behalf of those who have emailed, written and telephoned him for help. And for plenty of others who haven’t.

During what he calls “the dark old days” of apartheid, when travel bans, threats to his life and the killing of close friends were constant challenges to his faith, he never stopped praying daily for each cabinet minister of the white regime – by name.

The Archbishop’s decision to retire from the public stage following his 79th birthday will provide more time for prayer and reflection, he hopes; the democratic South Africa he helped to create is as much in need of his urgent petitions as ever.

He believes that its future is bright. “If I ever had doubts before about the possibilities of this country, they are now gone,” he says. “Truly. We are nothing less than a scintillating success story. That is our destiny.”

But before then, hard work is needed. “I am badgering everyone to put their obvious skills and desire for excellence to use for our own people and meet their great needs. It is what has kept their dreams alive and now it is time to deliver.”

In recent years he has directed the fearless moral challenges he once aimed at his apartheid rulers to the African National Congress, which has governed since 1994. Its leadership may now feel relief at his promise “to shut up, keep quiet, say nothing” once he bows out.

“The Arch”, as he is happy to be known, is vexed by what he sees as the enrichment of his country’s well-connected political minority, as well as its appalling crime rate and Aids pandemic – and has made no secret of his views.

On the day of my visit, mention of a possible new media law to curb journalistic freedom triggers familiar shrieks of indignation, wild hand gestures and the facial gymnastics for which he will be fondly remembered.

At first sight his suite of canary-yellow rooms in a nondescript business park could pass for the set of The Office. But a different story is told by the assortment of cartoons, life-affirming signs such as “We Don’t Believe in Miracles – We RELY on them!” and trophies bestowing the free world’s greatest honours for a lifetime of public service.

“The price of freedom is eternal vigilance,” the Archbishop says in his sing-song voice, setting down his cup which bears the legend “Growing old is inevitable, growing up is optional!”.

“But we are also learning that original sin does not recognise racial discrimination. During the struggle, we could boast that every one of us was altruistic and idealistic. No one ever said they were in the struggle to be rich.”

An apparently tireless campaign by the ANC to re-name the country’s cities, roads and airports in honour of its new political royalty has also tested the Archbishop’s patience.

“It is Mandela this, Mandela that and the Albertina Sisulu new fast road… and who else?” he demands, his short arms shooting heavenwards. “It’s as if the ANC were the only ones that exist! I must just feel grateful that my local airport is still called Cape Town international!”

And what if it were changed to Desmond Tutu International? “Then we really would be scraping rock bottom!” he answers quickly, howling with laughter.

“Of course, names that are offensive like Kaffirsfontein really ought to be changed. But Pretoria! They re-named it Tshwane, and then still referred to it as Pretoria. I am sad we are investing so much emotional energy in this. It is divisive and childish and… puerile, yes, puerile! Isn’t that such a lovely word?”

He sits back to take a restorative sip of his hot chocolate and reorganise a large wooden cross that has become tangled around his neck. The combined actions must have had a calming effect because he is suddenly reminded of another reason for hope.

“At one time people were squirming in their seat about our handling of the Aids crisis and stories about curing it by eating beetroot, and now they are giving standing ovations for our response. So that is very good turn of events,” he smiles.

The news of his reduction in workload, allowing him to “grow old gracefully” with Leah, his wife of 55 years, was met with resignation and sadness across South Africa, which was still coming down from the high of hosting the World Cup.

The sight of the diminutive priest, enveloped by his national team’s football strip, hat and scarf as he gave the most rousing speech of the tournament, confirmed his place in the world’s affections, which is matched only by that for Nelson Mandela.

But calls on his time have mushroomed in recent years, the more so as an increasingly frail Mr Mandela has faded from the limelight.

The Archbishop was treated for prostate cancer in 1997, the year after he retired as head of the Anglican church, and few expected him to return to such an unforgiving schedule.

In the decades of his steadfast campaigning against apartheid, he presided at the mass funerals of slain activists, and intervened with baying township crowds to stop them “necklacing” their enemies – putting petrol-soaked tyres around the necks of victims and setting fire to them. Throughout it all, he preached peace and forgiveness – setting him on a path to chairmanship of the historic Truth and Reconciliation commission which helped the new South Africa come to terms with its past.

The sight of him breaking down in tears during months of harrowing evidence was beamed around the world.

Only the Archbishop could have ever coined the phrase “the Rainbow Nation”. His gift for uniting enemies and calming fears led to his intervention in some of the world’s most intractable situations.

Robert Mugabe and the Israeli government are just two who have borne the colourful brunt of his conscience.

“All of those who have ever strutted the world stage as if they are invincible roosters – Hitler, Stalin, Amin and those apartheid guys; they (he breaks into giggles at the prospect)… they bite the dust.

“The universe can take quite a while to deliver. God is patient with us to become the God’s children he wants us to be but you really can see him weeping.”

Robert Mugabe once labelled him “that evil little Bishop” after being cautioned to give up power lest he find himself at The Hague war crimes tribunal. But, in the end, hasn’t the Zimbabwean despot seen the Archbishop off?

“Yes he has!” he replies. “But things will be OK in Zimbabwe. Great good comes out of suffering, even evil suffering.

“Take Nelson Mandela: so many people say ‘What a waste, imagine what he might have achieved if he had been freed earlier’. But he would never have been the person he is today without all of those 27 years in jail.

“He went to jail as an angry young man who believed that the very best white person was a dead white person.

“Those years were crucial in the making of the man who emerged. Suffering is an inescapable ingredient for people with magnanimity.”

Although he was only ever jailed briefly, the Archbishop has certainly known his own low points. The Soweto uprisings of the mid 1970s, his four children “being clobbered by those who wanted to clobber me” and the assassination in 1993 of Chris Hani, a popular communist and ANC leader, were the very worst of times, he says.

“When Chris Hani died, I wept like a baby, and Leah had to hold me like a mother. On occasion I have been very angry with God and given him ‘what for’. But God can only smile because only God can know what is coming next.”

The next chapter in the life of The Arch will be, he says, “all about keeping quiet”, drinking tea, watching cricket and “just being”.

On the strength of the evidence, it may prove his greatest challenge yet. As he sees me to the door, he demonstrates how firmly he can seal his mouth.

“I will be quiet, say nothing, no comment!” he declares, slamming his lips shut on his words.

His grey eyes begin to blink manically in a sort of Morse code, as if to compensate for the uncharacteristic silence. But inevitably, a rising swell of laughter soon breaks through his brief, failed effort.