By Audrey Brown BBC correspondent in South Africa

Mr Mandela holding the Olympic torch outside his former cell on Robben Island

He had warned us in 1997, when he anointed Thabo Mbeki to succeed him as president when his term ended in 1999, that he intended to step out of the limelight and live the life of a pensioner.

No-one really believed that he would fade from prominence because as arguably the most famous pensioner in the world - everything he does is news.

And since his latest retirement announcement, Mr Mandela does not seem to have slowed down a bit.

Workaholic

He was an Olympic torch-bearer when the flame came to Cape Town in June, en route to Athens.

He flew half-way round the world to deliver a major address at the UNAids conference in Thailand's capital, Bangkok, earlier this month.

Then he popped by to "greet" the protagonists involved in the Burundi peace talks, who were meeting in South Africa last week.

Mandela celebrated his birthday with wives, past and present

He also celebrated his birthday - quietly this time - but with a high-profile reunion with his ex-wife Winnie Madikizela-Mandela, who turned up at his rural retreat in the Transkei, to enjoy the festivities with him and his current wife Graca Machel.

He even edited the Afrikaans newspaper Beeld for a day in a special issue to commemorate his 86th birthday.

When he was given the freedom of the city of Johannesburg just a few days ago, he jokingly requested that he be allowed to drive his cows through the streets of the city of gold without having to pay taxes.

And this does not include the numerous phone calls and guests Mr Mandela receives every day. Let alone the places and people he decides to visit on the spur of the moment.

Those who've worked with him say quite plainly that Mr Mandela is a workaholic.

Hand-wringing

His ubiquitous personal assistant Zelda Le Grange said that retirement for Madiba, as Mr Mandela is affectionately known here, was for real this time.

She said he would be spending more time reading, waking up later than the usual 0500 and just relaxing.

MANDELA LANDMARKS 1918: Born in Eastern Cape 1943: Joins ANC 1964: Jailed for life 1990: Freed 1993: Wins Nobel Peace Prize 1994: Elected president 1999: Steps down Profile: Nelson Mandela

He is also meant to be writing the next instalment of his memoirs.

But when asked whether she thought Madiba really meant it this time - Ms Le Grange just laughed. And so did we.

Although we did believe that he might take it easier this time around. He is 86 and walks with difficulty.

But our concern for his health and well-being is not new either.

We've been worriedly wringing our hands since his release in 1990, when he took on a punishing schedule of meetings and travel, as well as the hectic negotiations which brought about peaceful elections in South Africa in 1994.

When he was diagnosed with prostate cancer in 2001, everyone believed once again that he would be forced to slow down.

This did not happen.

Instead, Mr Mandela completed his treatment, and as soon as he was given a clean bill of health by his doctors, he was again out and about, pronouncing on matters of great significance - like the time he accused US President George Bush of being "a president who can't think properly and who wants to plunge the world into a holocaust".

Years in jail

In fact, not a week goes by without Madiba being featured in the news.

He continued to initiate campaigns to fight against HIV/AIDS and he would invite tycoons on trips to rural areas and delicately manipulate them into pledging money to build schools and clinics.

At one time, President Mbeki was said to be exasperated by Madiba's hyperactivity.

But to their credit both men are gracious about each other, with Mr Mandela making a point of reminding everyone that Mr Mbeki is the president of the ruling African National Congress, and leader of South Africa.

Mr Mandela gave a helping-hand to Burundi's peace talks

Mr Mbeki's reported exasperation and the general concern for his health notwithstanding, Mr Mandela is clearly a man with lots of energy, insight and the drive to try and influence events in whichever way he can.

Perhaps Nelson Mandela has no intention of retiring - not if he can help it anyway.

Perhaps after so many years in jail for trying to make the world a better place and with his concern for world affairs, he is just not able to retire.

Perhaps he feels he has given up too much for too long to let other people just mess it up.

And he has spent much of his life at the very centre of one of the greatest stories of the twentieth century, so how can he retire?

Indeed, why should he retire?

He is Nelson Mandela after all.