[1][2] He was a member of a prominent Afrikaans family: his father and uncle owned Middelvlei, a successful wine estate in Stellenbosch, and were connected to politicians of the National Party (NP), which came to power in 1948.
He sold his share of Middelvlei to his cousin in 1963 and bought the nearby Neethlingshof Estate, another successful vineyard;[4] he also ultimately completed his bachelor's degree in history and economics.
[8] In 1985, still a full-time businessman, he called for its abolition, arguing that it had led the international community to view Afrikaners as racist and South African society as nearing extinction.
[9]Increasingly concerned about the South African political situation – partly as a result of trips to the United Kingdom, where he could read uncensored media reports – Momberg resigned from the NP in 1987 and became a founding member of the liberal Democratic Party (DP) the following year.
Momberg was a member of a wing of the DP which advocated for closer ties to the anti-apartheid African National Congress (ANC), a majority-black movement then banned inside South Africa.
[3] In April 1992, Momberg and four other parliamentarians – David Dalling, Pierre Cronjé, Jan van Eck, and Robert Haswell – were suspended from the DP after the party's leadership learned that they had recently held a private meeting with ANC President Nelson Mandela.
In a joint statement, the group said that they were responding to a call made by Mandela shortly after his release from prison in 1990, for "all our white compatriots to join us in the shaping of a new South Africa".
[6] Explaining his defection to the ANC, Momberg's colleague in the DP, Dene Smuts, later said:He had traversed the entire political terrain from the old establishment to the incoming new and he did so from the personal conviction that it was, for him, the right thing to do.
Although he had to endure abuse [from white conservatives], he did not for one moment, till the day he died, doubt that he had done the right thing and he received huge support from the real majority of the people of South Africa.
[6][1] After his death, his colleagues recollected the lengths to which he had gone to facilitate meetings among influential people of different political and socioeconomic backgrounds, with ANC representative Mosiuoa Lekota saying, "if there is a little equanimity in this House, it has quite a bit to do with the work that he did".
[13] Upon his departure from Parliament, Momberg was appointed by President Thabo Mbeki as South African Ambassador to Greece, with non-resident accreditation to Serbia-Montenegro, Bosnia-Herzegovina and Cyprus.
[2] He died on 7 January 2011 of heart failure, having collapsed at Longbeach Mall in Noordhoek after spending the day at a cricket test match at Newlands Stadium.