Born to an Afrikaner family in the Western Transvaal, Niehaus became involved in anti-apartheid activism as a student, joining the ANC underground in 1980.

Between November 1983 and March 1991, he was imprisoned on treason charges related to his activism, particularly an ANC plot to sabotage the Johannesburg Gas Works.

During this period, he frequently clashed with the ANC leadership over his outspoken support of former President Jacob Zuma and the Zuma-aligned programme of radical economic transformation (RET).

Niehaus was born on 25 December 1959 in Zeerust, a small town in the former Western Transvaal (now part of the North West Province).

[6] After his family moved in Johannesburg, he took church volunteering trips to Soweto, where, as a teenager, he was disturbed by the black residents' living conditions;[6] he later said that he came to believe that apartheid was heresy.

[8] Shortly before his final exams in 1980, Niehaus was expelled from Rand Afrikaans University for his political activities, including putting up Free Mandela posters on campus.

[11][5] Among other things, Whitecross was able to provide extensive evidence that Niehaus had been involved in reconnaissance of the Johannesburg Gas Works, apparently as part of an ANC plot to commit sabotage there.

[1] In 2008, LitNet published a blog by Niehaus – written in the form of an open letter to his young daughter – in which he described having been gang-raped by other detainees on the night before the Supreme Court convicted him in 1983.

According to his official biography, he was appointed to the ANC's Provincial Executive Committee in PWV, to its Negotiations Commission, and to the head of its national media liaison unit, where he served as spokesperson to Nelson Mandela.

[19] In late 1996, before the parliamentary term had ended, President Mandela appointed Niehaus to succeed Zach de Beer as South African Ambassador to the Netherlands.

[23] Upon his return to South Africa, Niehaus became executive director of the National Institute for Crime Prevention and Re-integration of Offenders (Nicro) with effect from 1 June 2000.

[4] In 2001, Niehaus left NICRO to become a partner at professional services firm Deloitte & Touche, which at the time was launching a Dutch desk.

[29] He resigned from that position in 2003, and thereafter held a series of short-lived positions: the South African Presidency contracted him to work on its Decade of Democracy celebrations in 2004; he was CEO and spokesperson of Ray McCauley's Rhema Church from 2004 until his resignation in 2005;[30] and, finally, he was CEO of the Gauteng Economic Development Agency (GEDA), a department of the Gauteng Provincial Government, for the last seven months of 2005.

[34] In 2017, he resurfaced as national spokesperson for the ANC-affiliated UMkhonto we Sizwe Military Veterans' Association (MKMVA) and as a frequent commentator on ANN7.

[37] He also used his personal and MKMVA platforms to defend corruption-accused former President Jacob Zuma,[38][39] to attack the ANC's leadership,[40][41] and to promote an ideological programme of so-called radical economic transformation.

[48][49] While Niehaus awaited his disciplinary hearing, he was also fired as an ANC staffer: on 9 September, he was summarily dismissed from his position in the secretary-general's office after he made another provocative public statement.

[57] Less than a month after his expulsion from the ANC, in a Twitter Space on 11 January 2023,[58] Niehaus announced the launch of the Radical Economic Transformation Movement (RETMO).

[59] The movement was formed to lobby for radical economic transformation, and Niehaus, as its chairperson, outlined a ten-point policy platform that included land expropriation without compensation, opposition to the privatisation of state-owned enterprises, and stronger border policing.

[67] In February 2009, the Mail & Guardian's Pearlie Joubert published a lengthy exposé about Niehaus's "broad trail of bad debt and broken promises".

[31] In the same article, confronted by Joubert, he confessed to a series of improprieties, admitting that he was a serial overspender and had left his last few jobs – at Deloitte & Touche, Rhema Church, and GEDA – due to mismanagement of his personal debt and continued borrowing.

I asked people like Saki Macozoma, Cyril Ramaphosa, Tokyo Sexwale, Gill Marcus, Pallo Jordan and Rick Menell to help me financially.

[33] Meanwhile, other media houses launched their own investigations into Niehaus's affairs and published new allegations, including that he had falsely claimed his sister had died in order to obtain business-class airfare from a law firm where he done BEE consulting,[70] and that he had falsely claimed to have leukemia in order to obtain a free holiday to Mauritius from a travel agency.

[71] The Times estimated that he was more than R4.4 million in debt,[72] though ANC-affiliated businessman Vivian Reddy said publicly that he would provide Niehaus with financial support.

On 1 May 2012, he gave his first interview since the February 2009 scandal, appearing on John Robbie's Radio 702 talk show to announce that he had repaid all his debts and expected to be appointed to "a formal position" in the ANC administration.

[75] The ANC denied the latter claim, and several creditors came forward to dispute the former, including Deputy Minister Derek Hanekom,[76] ANC-affiliated trade union SACCAWU,[77] and Niehaus's former landlord in Midrand.

[85] In 1986 in Pretoria Central Prison, Niehaus married Johanna "Jansie" Lourens, who was imprisoned alongside him in 1983; they had met at university, where she had recruited him into the armed struggle.