Revealed: The Secrets of an African first lady

It was once written that if African leaders past and present were rounded up and tossed into a blender then the resultant Big Man would look like this: "His face is on the money. His photograph hangs in every office in his realm. His ministers wear gold pins with tiny photographs of him on the lapels of their tailored pin-striped suits.

He names streets, football stadiums, hospitals and universities after himself. He carries a silver-inlaid ivory mace or an ornately carved walking stick ... He insists on being called 'doctor' or 'conqueror' or 'teacher' or 'the big elephant' or 'the number-one peasant' or 'the wise old man' or 'the national miracle'."

Blaine Harden wrote that nearly 20 years ago but the American writer's sharp observation has not been bettered. There should, however, be an addition – the Big Man's wife. Her face is rarely seen in public, except on state occasions. Her custom is welcomed by Europe's premier plastic surgeons. Her shopping trips are national legend. Her foreign retail adventures involve requisitioning the national airline. She agrees to the sacred rule that her children get official first family status and she keeps her mouth shut about everything else. From the Mobutus to the Mugabes the vow of silence was unspoken and unbreakable.

Then along came Oluremi Obasanjo. The first wife of the former Nigerian president Olesegun Obasanjo has broken it in spectacular style with a tell-all autobiography, Bitter-Sweet: My Life with Obasanjo. The author paints a portrait of her husband as a vindictive "master of decoy", a "violent and unrepentant wife-basher", and a man whose "womanising knows no bounds". It couldn't come at a worse time for the 72-year-old Mr Obasanjo who has been busily building a new profile for himself as a pan-African statesman second only to Kofi Annan.

The former general, who has had two stints as Nigeria's biggest Big Man, once as a military ruler from 1976-9 and then as elected president from 1999-2007, is more often seen these days as the United Nations envoy to the Democratic Republic of Congo. His credentials as a continental statesman are regularly burnished by Western leaders and he was a particular favourite of neo-cons like Donald Rumsfeld. This was supposed to be the time where the retired general enjoyed the fruits of his wisdom in becoming the first Nigerian leader to surrender power peacefully – albeit after failing to change the constitution to get himself a third term in office.

Instead, the warts-and-all account of his life is a best-seller in Nigeria and public interest has been so high that the daily newspaper The Vanguard ran a successful serialisation. So far, the Big Man himself has kept his peace, leaving friends to dismiss the author, known as Mama Iyabo after the first of their five children together, as a typical woman scorned. What makes Bitter-Sweet hard to dismiss though is the flattering portrait she paints of the young Obasanjo.

The pair met while she was at school. Only 11 at the time, the middle-class daughter of a station manager on the colonial railways, she recalls being confronted by a supremely confident young boy who "wore no shoes, not even the cheap tennis shoes sold for seven shillings and six pence that students wore then". The future president was penniless and "washed desks in school and worked as a labourer to make ends meet". During their eight-year courtship the initially shoeless Obasanjo excels at school, joins the military and rises rapidly through the ranks, surviving being taken hostage while serving as a peacekeeper in the DRC. The high point of the romance came in a register office in Camberwell Green, where the two were married in 1963.

She traces the end of the happy days to the gift of a gold pendant in 1970. "My Remi, man spoils good things," the inscription read. "He knew he had started to cheat. I did not understand the import of the message because I was so busy raising my young children and pursuing my career ... How I wished his recognition of his guilt of cheating on me had checked him of his monumental moral indiscipline that was to smear our marriage."

What ensues is an almost slapstick riot of affairs and breathless high politics punctuated with domestic violence and desperation. And it's one in which Mama Iyabo is happy to name names. In the early 1970s her particular nemesis was an older married woman called Mowo Sofowora. One evening, she recalls: "I was eavesdropping on the phone downstairs while Obasanjo was in the bedroom. They had spoken for about 30 minutes when she then said she was having a headache. I had heard enough, so I butted in: 'It's that headache that will kill you, shameless married woman dating a younger man'. On hearing my voice, Obasanjo charged downstairs to beat me and we had one of the many fights that had come to define our marriage."

On another occasion Oluremi Obasanjo, now pregnant, was surprised to hear a nurse at the hospital announcing that Mrs Obasanjo was coming in with her sick children. "Lo and behold, she [Mowo] soon appeared with Busola and Segun, my children. I removed my head tie ... and lunged at her. 'Mowo, Oko ni o gba, o le gba omo mi,' I screamed, meaning: 'You may snatch my husband you can't snatch my kids.' I slapped and punched her. It was a spectacle. The hospital was turned upside down. I ran after the car that brought her, smashed the side glass." Surprisingly she reserves no particular ire for Stella Adebe-Obasanjo, who would go on to be the general's third and most notorious wife, eventually dying while undergoing liposuction in Spain. She describes Stella as just another in "the stable of Obasanjo's many ponies. Her problem was that she was too showy and lacked self respect. During our tempest, she would telephone me to announce that she was in complete control of my husband." In addition to the string of affairs, including one with a wife of another Big Man, the Nigerian dictator Sani Abacha, she reveals an extraordinary fallout with Murtala Muhammed, the brigadier he would later succeed in 1976 as military ruler of Nigeria. Muhammed's mistake was to reprimand him over his treatment of his wife: "Obasanjo was enraged that Muhammed was telling him how to take care of his wife. So, he grabbed Muhammed by the collar, in the presence of other officers, and challenged him to a duel."

Oluremi Obasanjo separated from him in 1975, one year before he would inherit power from Muhammed, who was murdered in one of Nigeria's many abortive coups. She recalls having a shouting match with another of Obasanjo's mistresses on the phone when he "pounced on me and began to curse and punch". The general then chased her with a knife and she fled the house. Left with nowhere to live she complained to leading members of the government, which in turn prompted the near duel with Muhammed.

Far from taking a massive risk on the incendiary book, it turns out that Diamond Publications in Lagos was indemnified by the author herself. She was so confident of her accuracy, Mrs Obasanjo the first said: "If anybody feels aggrieved by what I have written they should write their own book or take me to court."

The publisher, Lanre Idowu, is delighted. "It is the story of love and betrayal, of dedication and indifference, of tender love and brutal nonchalance, of great expectations and monumental disappointments. It is the story of a wife and mother, a participant-observer who witnessed many things about the nature of power – its allure and misuse."

Traditionally the public in much of Africa only gets to know about the private lives of their politicians through rumour, gossip or, in the case of Kenya, by glorious accident. Kenya's President, Mwai Kibaki, had enjoyed the pretence of a single Catholic marriage until December 2004, when the vice president publicly toasted Lucy Kibaki as the "second lady": it emerged that the Kenyan President had a second wife – Mary Wambui – and the original Mrs Kibaki was very unamused.

Kenyans were treated to a very public war of the wives which washed over into the media. The notoriously fiery Lucy – who five months later would burst into state television in her pyjamas and assault a cameraman – issued a statement demanding no further references to "purported" family members. But Wambui's family hit back with photos showing the President paying a dowry to the family.

In Zimbabwe there is less to laugh about. Grace Mugabe, Robert's second wife, has become a national hate figure, notorious for her extravagance during the most dramatic collapse of an economy during peacetime ever seen. Yesterday she stoked fresh outrage by withdrawing a reported $92,000 from the central bank to fund a family holiday in Malaysia.

The final word of course should go to Mama Iyabo, who says that it's about time more people followed her lead: "The public deserves to know a lot more about the experiences of public figures beyond the advertised public appearances they see. If my work has succeeded in doing so, we should look at it as expanding the democratic frontiers of free flow of information. Nigeria and Nigerians need to shed the culture of undue secrecy about public figures and public affairs."