Frost holed a birdie from 16 feet on the 18th hole for a 36-hole total of 3-under-par 141, one shot better than Andre Bossert, Douglas McGuigan and Tjaart van der Walt, who went to a sudden death playoff to determine the remaining two spots.
Bossert claimed the first place with a par on the 10th hole, before Scotland's McGuigan was handed the chance to make first major appearance five holes later when Van der Walt, a qualifier here last year, missed a 3 foot par putt on the 18th green.
While the playoff unfolded, the 45-year-old Frost was reflecting on his success in the safety of the clubhouse, thinking ahead to his first appearance at the Open since 2000.
'I'm looking forward to going to St. Andrews. There's a nice ambience there and I know the golf course very well,' said Frost. 'I've played there over 150 times and I've played a lot of dunhill cups there over the years.'
Despite making a nine at the par-4 fourth hole, Frost salvaged a 4-over-par 76 in the howling wind, a score for which his putter was most responsible in putting together.
'I holed about an 80-footer on the second and made a few other long putts today,' said Frost. 'The putt on 18 was about 15 feet and holing that was very important.'
McGuigan, who represents Scotland but was born in Durban and raised in Kimberley, played his back nine in 1 under par and thought he had avoided a playoff when he two putted the last for a 73 and a clubhouse score of two under.
'I thought I was in, but found out I had to go back out there' said a visibly exhausted McGuigan. 'That playoff was really though but it feels stunning now. We were talking about it and saying this is probably the biggest pre-q out there. That was definitely the biggest pre-q of my life. It's brilliant.'
'After winning the Platinum Classic (in 2003) it's been a bit of a disaster. I had surgery on my shoulders and I haven't played well, so this is a hell of a confidence booster. I couldn't ask for a better way to start the year.'
Bossert simply had to qualify, having missed out by two shots or less on more than five occasions since he made his debut at the Open at Turbnberry in 1996.
'It was a huge relief to leave the playoff so early,' said Bossert. 'Because I'm feeling tired, the guys are younger than me. I thought the quicker I get out of here the better. I had a feeling I might get in though.'
Southern Africa PGA Commissioner, Johan Immelman, expressed his gratitude to the Royal & Ancient for making the spots available and bringing a tournament of this calibre to South Africa.
'This is such a wonderful opportunity for our members to gain access to the oldest and most prestigious Open in the world. We hope our graduates continue the magnificent record at the event.'