Today marks the twentieth anniversary of former President FW de Klerk's historic announcement to unban the African National Congress (ANC) and free Nelson Mandela, who was a political prisoner at the time.

On 2 February 1990, de Klerk announced in Parliament: "I wish to put it plainly, that the government has taken a firm decision to release Mr Mandela unconditionally. I'm serious about bringing this matter to finality without delay. The government will take the decision soon on the date of his release."

Nine days later, Mandela walked out of prison a free man. This lead to South Africa's first democratic election in 1994, in which Mandela was elected as the country's new President.

In an interview with a local South African radio station on Tuesday, the former President recalled how his announcement shook the nation and stunned those sitting on opposition benches.

Apart from a few select ministers, the full Cabinet was only informed two days before the speech was delivered, he explained. At one point there was silence in the house, and he had at some point repeated himself.

At the time he was convinced that he was doing the right thing for the country. "As I walked into Parliament I knew my announcement would change South Africa forever."

Mandela's wife at the time, Winnie Madikizela-Mandela, said that the day was a fulfilment of a dream and that the family had been completely overwhelmed.

"We were ecstatic because I knew the history of our country would never be the same," she said, also speaking to the news radio station.

The FW de Klerk Foundation will celebrate the twentieth anniversary with a conference at the Council Chamber of the Cape Town Civic Centre later today, culminating in a gala dinner.

In a statement, the foundation said: "For white South Africans, the announcements of February 2, 1990 signalled their willingness to end centuries of alienation and division by abandoning the dominant position they held for more than 300 years.

"For black South Africans, it heralded the dawn of a new age of dignity, equality and full political rights for which they had struggled for so long.

"For the world, these historic events showed that even the most intractable disputes could be resolved peacefully by negotiations and goodwill."

The foundation is expected to launch a limited edition coffee table book titled South Africa: 20 Years Later.

The conference will be addressed by among others, Western Cape Premier Helen Zille, former Chief Justice Pius Langa as well as de Klerk.