Fast bowling is a tough business. A tough, serious business. Think of Gus Fraser, trudging back to his mark with a face as long as Livery Street. Or Jimmy Anderson, scowling his way through another spell. And who can blame them? Invariably fast bowlers have spines held together by plates and screws, toe nails that come off in their socks and blisters as large as a side of bacon. They're kept going by a diet of physio and pain killers. Their future is full of hip operations and micro-fracture surgery.

But, at almost every moment of this Port Elizabeth Test, Mark Wood has had a smile on his face. Before his overs, he's run up to the umpire to give him his hat or jumper, much in the way you see excitable children act when they start playing cricket. And between deliveries, he's thrown the ball up in the air to give himself catches, much in the way you see excitable children act when they start playing cricket. Often, in delivery, his commitment is such that he hurls himself off his feet. And ahead of play, he ran over to the traditional musicians who were entertaining the crowd to have a go on their drums. All while wearing a broad grin. Much in the way you see excitable children…

And you can understand why. For Wood has spent more of his career in rehab than a Hollywood star. He's undergone numerous operations on his ankle and, since his last competitive match - on July 14 - had knee surgery and endured a lengthy period on the sidelines due to a serious side strain.

ALSO READ: England surge towards victory on Root four-wicket haul

It's worth looking back on the moment that injury was incurred. It was the World Cup final. The 45th over of the New Zealand innings. Wood, who had defied all the predictions to play in 10 games in the tournament, was mid-way through his final over when he felt sharp pain in his side. He knew, in that instant, he was in trouble.

He could have stopped bowling. Had he done so, he might still have had an outside chance of returning before the end of the Ashes. But the game was in the balance and he didn't want to let his team, his captain, down. He completed his spell. The last two deliveries, with no thought to his own welfare, were bouncers. The pain worsened considerably.

"I had three balls left," he recalls. "And every ball I bowled it got worse. I knew it was pretty bad. But it's a World Cup final and I didn't want to limp off after 9.3 overs. I spoke to Eoin Morgan about going through those three balls, but I knew I was out of the Ashes."

So Wood will never take moments like these - representing his country, tearing in and unleashing whole spells of 90 mph deliveries - for granted. He knows such experiences are precious and fleeting. He knows it could be over at any moment.

"I'm just trying to enjoy it," he says. "I'm just trying to have fun, take it all in and play with a smile on my face. It's been a lot of fun.

"I love it. I've waited quite a while to come back. July was the last game I played and, with the way my body has been, it's something you can't take it for granted. This could be my last game.

"I'm not just hoying [throwing] out clichés. That's genuinely how it is. I have to take it as it comes because that's the nature of how I bowl. Tomorrow I could fall over for the 54th time in the game and strain my ankle or something like that.

"I'm just about patched together. I'm wrapped up like a mummy on my left leg. Something is going to hurt eventually but it's part and parcel of being a fast bowler. I'm not a natural. I'm not 6ft 5in and built like a tank, so I have to give everything I've got to try and rev it up."

Now there will be those, reading this piece, who look at the scorecard and wonder what all the fuss is about. And it is true, at this stage, Wood only has two wickets. And while he has also seen a chance or two put down, struck five sixes in a brisk 42 that helped set up the declaration and plucked a fine catch out of the air - "I made a bit of a meal of that," he says bashfully - the fact is there have been other, far more eye-catching individual performances in this match.

But in a team game like this, we cannot be judging the value of players' contributions simply by the scorecard. The truth is, Wood has bowled at a pace - somewhere around 94 mph at his quickest - that has brought a new edge to this England attack. Some of the South Africa batsmen - notably Zubayr Hamza - have looked horribly unsettled by him. And, while there is no way of proving it, you suspect Wood has, in both innings, helped create chances at the other end as rattled batsmen struggle to retain their composure. You suspect his value is far greater than the number of wickets he has so far taken.

"I like the word 'assists'," he says, while trying to explain his contribution. "I think it's good to bowl in a partnership."

The wicket of Dean Elgar will have been especially rewarding, though. Elgar is probably, at this stage, the best player of pace in the South Africa side. So to set him up with a spell of short balls and then send his off-stump sent cartwheeling with a rare full delivery that may have left him a fraction provided more tangible rewards than the slaps on the back from appreciative teammates.

"Every fast bowler wants to see a stump going flying," he says. "And that was a great feeling. And one that really helped with my confidence. If you don't get a wicket you're thinking 'I need to try and prove a point; I need to show my value and keep my place in the team.'"

You could argue - and you may well be right - that Wood overdid the short ball here. In the second innings, 41 of the 66 deliveries he has so far bowled have been short or back of a length. Only two have been fuller than a length. For a man capable of swinging the ball - both conventionally and reverse - that seems like a bit of a waste. He's better than playing the part of a simple enforcer.

Incidentally, that final spell was six overs. It's too long for a bowler of Wood's pace and fragility. Mitchell Johnson, at his very best, rarely bowled a spell longer than three or four overs. England could learn from that.

But those were the orders and he's a team man. "You do what is best for the team," he says. "I noticed my pace dropped off a little at the end. But when you're bowling bouncers all the time, it takes it out of you."

Wood's career stats are, in the grand scheme of things, fairly unremarkable. This is his 14th Test; he has one five-for and an average of 36.81. But we should probably distinguish Wood's statistics before he lengthened his run-up and afterwards. Before that change, there was a lot of talk about his pace, but not much evidence. He routinely bowled in the mid-80s and he routinely underwent ankle surgery.

But since the end of 2018, when he made the decision to lengthen that run, he has bowled with consistent pace and hostility. The only other Test he featured in since then included his career-best performance - he was player of the match after dismantling West Indies in St Lucia - while his World Cup spells included the fastest delivery of the tournament and meant that only four men claimed more wickets. Just as importantly, the longer run appears to have taken a bit of stress off his body. But for that side strain - the knee was more of a clean-up job than anything especially serious - his body (and most crucially, his ankle) has stood up pretty well to the exertions.

For that reason, there is hope he could appear in the fourth Test next week. And with Jofra Archer now bowling again in training, there is a possibility that England could field both their fast bowlers on a Johannesburg pitch which has, at times, been rated among the fastest in the world.

"I'd love to play there," Wood says. "I've never actually played a match there, but I trained there once and the ball flew through. I'd love to have a go there."

The word "love" comes up a lot in Wood's conversations at present. He says he "loved" his batting, "loved" how well Ollie Pope batted and Dom Bess bowled and "loves" being back in the team and "doing something I really enjoy".

The result is that, if the weather relents - "I thought Africa was the sunniest place in the world," Wood mused, "but I come here and it's just like Durham," - England have a great chance of achieving back-to-back victories in South Africa for the first time since January 1957. To put that in perspective, Winston Churchill's second spell as Prime Minister had just finished. It's a significant achievement.

So was the gamble to keep bowling in the World Cup worth it?

"Absolutely," he says with feeling. "I'd take being a World Cup winner even if I didn't play another game of Test cricket. I would not swap that for the world. I've always got that to look back on. It was the pinnacle of my career."

He's probably right. But to see him throw himself into his work again at Test level, to know how hard it's been to get back to this level, to appreciate how much better England's attack looks when he is part of it and to witness his uninhibited enthusiasm… you rather hope there are a few more Tests left in Mark Wood yet.