Towards the end of the warm-up game in Benoni a few days ago, Chris Woakes approached James Anderson with a bewildered look on his face. How was it, Woakes wanted to know, that after all this time and all those overs, that Anderson - now aged 37 and with nothing left to prove - was still as enthusiastic as ever.
It was a reasonable question. It was, even by the standards of modern warm-up games, a pretty tame affair. It didn't carry first-class status, there was no prospect of a result and, in the end, the captains decided to call it a day not long after lunch on the final day.
But somehow, for some reason, Anderson was as excited as ever. Maybe because it was he had been starved of cricket for several months. Maybe it was because an international return was now so close he could taste it. But at the point where everyone else was counting down the clock, Anderson was like a puppy chasing pigeons. Still cricket crazy.
"We were taking the second new ball on the third day and I couldn't wait," he says now. "Chris Woakes asked me why I was still so enthusiastic. He was saying 'what part of this do you enjoy? I'm aching, I'm stiff.'
"But that's what I love about it. You wake up the next day, you struggle to get out of bed and walk to the toilet. You know you've put in a shift. I get satisfaction from that.
"I'm still hungry to play. I still feel like a kid. It still feels so special putting the England badge on."
"I'm 37 but I still feel like a kid. I'm still diving around like a kid, trying to catch balls like Ben Stokes at the World Cup"
That probably explains why Anderson will - late injury or illness permitting - gain his 150th Test cap in Centurion on Boxing Day. Only eight men have previously reached the 150 Test landmark. None of them were specialist bowlers (though Jacques Kallis' record of 292 wickets demands huge respect) let alone seamers. The record - to go alongside the one for the most Test wickets taken by a seamer and the one for the most deliveries bowled in the format - is testament to his desire and determination as much as his skill.
He could have been forgiven for retiring at the end of the summer. The calf injury that limited him to the briefest of cameos in the Ashes had proved more stubborn than anticipated. The prospect of months of lonely gym work and rehab would have put off many at his age. He has the prospect of lucrative media work ahead of him and might want to protect career statistics that long ago passed through decent, waltzed past remarkable and settled into incredible. He is, after all, three-years older than Vernon Philander, who announced his imminent international retirement this week, a year older than Dale Steyn, who played his last Test at the start of the year, and two-years older than Morne Morkel, who long since moved into greener pastures.
So what drives Anderson on?
"I still think I've got something to offer," he says. "I'm still bowling well. I was watching the guys doing catching practice today… I'm 37 but I still feel like a kid. I'm still diving around like a kid, trying to catch balls like Ben Stokes at the World Cup. That sort of thing keeps me going and keeps me wanting to play."
It's always been this way, though. Whether it was the stress fracture in the back in his early 20s, the shoulder problems in his mid-30s, or the calf, side or groin strains that have cropped up along the way, he has always found the hunger to claw his way back into the game. Put simply: he fell in love with the game at a young age and that love shows no sign of fading.
"If I do play in Centurion," he says taking nothing for granted, "it will be a really proud moment for me. Not many people have played 150 Tests for their country. It makes all the hard work throughout my career, the ups and downs, the times in my early 20s when I didn't know if I was ever going to get picked again or get another wicket, worthwhile."
He remains fiercely competitive, too. One former England team-mate, emerging scratched and bruised, spoke of his surprise at how seriously Anderson takes the inter-squad football that still, despite Ashley Giles' reservations, precedes nearly every training session. Even on Christmas Eve Anderson looks crestfallen when his side concede a goal. He doesn't know how not to care.
"You've got to have that fire to get through rehab," he says. "It can be dull as ditch water; the monotony of the daily exercises you've got to do to get back to full fitness. It's been so frustrating for me trying to get back to full fitness. Without the hunger to play international cricket you're not going to get through it."
"You look at people like Jamie Vardy getting faster in his 30s. Why should people start slowing down and getting slower just because the number next to your name keeps going up?"
He describes central contracts - still a new initiative at the start of his career - as "a Godsend" and accepts bowlers of an earlier age were not so fortunate.
"I don't think I would have got anywhere near to the figure I'm at now without a central contract," he says. "They have been crucial. Lots of people were talking about Bob Willis and his career recently. He played for England and then, two days later, he'd be back playing for his county. It was brutal. So once central contracts came in it was a Godsend for the bowlers.
"Most cricketers I speak to say 'you're a long time retired'. There's lots of players who've had to retire early through injury that would have loved to carry on. So I feel privileged in the way I've got a good body and a good action that is repeatable. Injuries haven't really plagued my career. I feel lucky in that respect. I want to make the most of what I've got. As long as I feel I can keep taking wickets at this level then I'll keep trying to improve."
All of which begs the question: how much longer can he go on? The question clearly frustrates him and he probably has a point in suggesting it is posed only due to his age, not his performance.
"The only reason people feel I should stop is because you get to that age - 34, 35 - and people start asking if you're thinking about retiring," he says. "Yes, I've learned I can't come back from muscle injuries as quickly as I thought I could. As you get older they take longer and that's what I've needed. I've needed a few months to really get back up to speed.
"I'm not even thinking about retirement. I'm just thinking of improving. I can get better; I can improve. You look at people like Jamie Vardy getting faster in his 30s. Why should people start slowing down and getting slower just because the number next to your name keeps going up?
"I feel great. I feel like I can still run in hard and dive around in the field. I don't feel like I'm ageing horrendously quickly. I feel good and I want to keep enjoying being around the group."
"It makes all the hard work... the times in my early 20s when I didn't know if I was ever going to get picked again or get another wicket, worthwhile" James Anderson on getting to play 150 Tests
Could that include another Ashes tour?
"God, when's that?" he laughs. "Two years? I've not even got half an eye on that, really. I've both eyes on this week. I really want to put in a performance.
"There will be things coming up in the next few 18 months or so. Do I go to Sri Lanka if the pitches are like they were last time? Is there any point in that? Might it make sense to keep me fresh and keep me going as long as possible? That's what I'm keen to do. And if we can do that, I don't see any reason why I can't make that [Ashes series]."
He admits there was a period in his early 20s when he thought he may never win another cap. But, apart from a spell in the ticket office at Burnley Football Club as a teenager - "I got to meet Ian Wright," he says, "that was the highlight" - he has never needed to look for a 'real' job.
"I was clueless," he says. "But if I hadn't made it as a player, I still wanted to go into sports. I thought I'd go into sports journalism which just seemed pretty easy." The last line is delivered deadpan, but with just the hint of a smile.
A few hours later, as one of the longest training sessions in England's recent history came to an end, Anderson trudges off the pitch past a small group of journalists. "You'll notice we're still working," one of them says. "This journalism thing is harder work than it looks." He nods appreciatively. One hour after that, as the last journalists leave the ground, Anderson walks past one more time. This time padded up for a net. The last player left at training. "It seems I'm working the longer day," he smiles.
That's Jimmy Anderson: still cricket crazy after all these years.