18 January 1989
On 18 January 1989, P W Botha suffered a mild stroke at the age of 73. He was scheduled to meet with Namibian political leaders on 20 January 1989, but could not attend the meeting due to his ailing condition. Acting president, Christiaan Heunis, attended the meeting in his place.  Some sources say that the stroke left him partially paralysed, but despite his health, Botha refused to resign and was subsequently ousted from office by members of his own party. Even after the party's actions, he persistently retained the presidency amid rumours of his resignation.
References

Kalley, J.A.; Schoeman, E. & Andor, L.E. (eds) (1999). Southern African Political History: A Chronology of Key Political Events from Independence to mid-1997, Westport: Greenwood. (From Archive)