Stephen Cook should have been nervous. Jimmy Cook was not.

He watched his oldest son walk out to the middle, as he has done for the best part of the last two decades. He watched him take his guard, perhaps with a little more care than he used to do two decades ago. He watched him prepare to face the first ball, a ball that would be unlike any other in the last two decades because it was the first of a Test match. And then he watched Stephen wait.

It was only 10:28. The game could not begin until 10:30. That was enough time for Cook senior to relive the first ball he faced in Test cricket - a beauty from Kapil Dev that he edged to the cordon at Kingsmead which came at the age of 39 after South Africa's readmission - and for Cook junior to remember his father's pre-match joke.

"You haven't got much to beat here, boy. You've only got to last two balls and then you'll be fine."

Then it came. With a ribbon on it. A leg-stump half volley from James Anderson which Stephen could lean into and lash to the square leg boundary. "He got a nice ball. He couldn't have asked for a nicer one," Jimmy admitted, a few hours later as Stephen entered the eighties.

Even then, Jimmy maintained he had no reason to be nervous. He was just happy to be in attendance.

"I wasn't supposed to be here because a while back I had organised to go and do some coaching at Gary Kirsten's academy in Dubai with my younger son Ryan," Jimmy said. "Suddenly when Stephen's call up came, Ryan said to me, 'You'd better stay here,' but because we had already made the commitment, I still thought we needed to go. Ryan told me to think about it but even after thinking about it, I still thought we should go. Then Ryan told me I couldn't go because he had cancelled my ticket."

At least Kirsten understood. "He sent me a message from Dubai and said, 'Not a problem. you've got to be there on the day'."

So there Jimmy was. In Suite 32. Watching. Without any nerves.

"If Stephen was 18, I probably would have wondered, 'ooh what's going to happen here,' but the guy's has been around the block. He has played 15 years in the first-class game so he knows how to look after himself," Jimmy said. "They [England] might well have chirped him this morning but it's nothing he hasn't heard. A younger guy might have been listening more and thinking about it a bit more."

Experience is really why there were so many calls for Stephen at the start of the series. South Africa had just returned from India, smashed. They needed several changes to restore confidence, specifically a specialist opener but chose to give regular No.3 Stiaan van Zyl a chance to prove himself at home. That chance extended even when Stephen, the highest run-scorer in last season's first-class competition, opened his account this summer with two centuries in two games.

After a childhood spent in the shadows of Graeme Smith, with whom Stephen opened the batting at school with and who Jimmy says "was always better than Stephen," and an adult career being constantly overlooked, Stephen could easily have given up, especially as he had other options. He has a law degree and his wife has a British passport. There were times when Jimmy urged him to make use of both.

"I told him maybe he should go overseas. He said no because he wanted to play South Africa," Jimmy said. "I told him that maybe he was getting on a bit. He still said just kept saying, 'I am telling you that I am going to play for South Africa.' He never thought the door was closed. He has persevered really well. He has been dedicated, he kept fit and kept going even when it looked like it wasn't going to happen."

When it did happen, Stephen made sure he made it count. He was helped by some lacklustre bowling from an England attack who, with the series won, were not as aggressive as they have been throughout the series. He was able to form a solid opening stand with a Smith-like partner in Dean Elgar, another with one of the senior-most members of the side, Hashim Amla, and to set South Africa up, as he does his franchise team.

Elgar's batting style is similar to Smith's, which may mean Stephen will complement him in the same way he used to Smith. "Graeme was the strong, bang, bang, bang guy who used to hit fours. Stephen was the technical, smaller guy," Jimmy, who was also their coach, said. "As a youngster, he was not about blasting fours all over the place, he used to look for a single there, single here and then if he got a bad ball he'd put it away for four. They were a nice contrast to bat together. Graeme was the real aggressor, Stephen tended to be the steadier accumulator of runs."

A freak catch meant Elgar was not around long enough to properly test that theory but there should be other chances. Cook must get a decent run in the side, even though the next Tests are six months away. Even if van Zyl and Rilee Rossouw, who has been promoted to opening the batting for the Knights, set the first-class scene alight. Stephen's time is now and the confidence he inspires at the crease has earned him that. "Their time will come," Jimmy said.

His innings was a combination of all the right things. He was strong off the pads with the flick, assured in his defence and unruffled when things got tough. And they did. When he was on 47, Stephen was dropped by Jonny Bairstow. He responded with the cover drive that took him to 50. When England tightened up after tea, Stephen was more cautious too. The bowlers found some swing and he negotiated it well. When he was 98, Amla played on leaving him with a new partner and England reviewed an lbw decision against him, which replays showed was clipping leg but enough to overturn the on-field call.

As the television camera panned from the field to the father, there should have been some nerves. Jimmy will deny it because he knows this: "The disciplines were instilled in him from a young age: you don't get out because you are tired. You can play a bad shot or get a good ball but don't get out because you are tired," Jimmy said.

Stephen didn't falter before three figures. His dad and his team-mates willed him on as he raced through for two to become the sixth South African to score a century on debut and the fourth-oldest overall. Stephen celebrated with satisfaction. Jimmy did not look surprised at all.

Firdose Moonda is ESPNcricinfo's South Africa correspondent