For a couple of weeks last autumn, Andy Farrell did something strange. He became a normal fan and a normal dad.
Ireland had just been knocked out of the World Cup, but when the players returned home the new head coach remained in Japan with his wife Colleen and family to watch their eldest son, Owen, play in the semi-final and final.
Had things worked out differently, the former England international would have been in the opposition camp for the semi-final, but circumstances dictated that England took on the All Blacks.
So Farrell Snr took his seat in the stand at the International Stadium in Yokohama and watched as his son stood up to the haka and then led England to perhaps their greatest performance.
And then, a week later, he was on hand to watch his son endure a very different experience as England lost to the Springboks at the same venue in the final.
Tomorrow week, he'll be back in the coaching booth at Twickenham and will spend much of the week working out how to shut a backline down that is run by his son.
That, he says, is something he finds perfectly normal.
But watching him play in Japan was a very different experience.
"Now that was tough. I was back to being a parent again and that is tougher than being a coach against your son that is playing on the opposition," he said. "I actually did the whole fan, family thing that day on purpose, to get back to how it felt before all this even happened.
"But this is totally different. Totally different to that."
What, we ask, were the emotions he felt as he watched England produce that scintillating performance?
"Well, you want your son to perform, don't you? You speak to any parent who is watching their son play for Ireland at the weekend, your fingers are crossed, hoping it goes well," he explained.
"When you're a coach, you don't feel like that. You don't hope it goes well, you're assessing things and you're seeing how the plan is coming together. So you're busy in your mind as a coach, you've got a distraction.
"But, when you're a parent, and I'm sure all parents would tell you the same, you're just watching your son. You're not watching the game as much as you would do as a coach."
At Twickenham, it will be different.
Farrell Jr and Farrell Snr once shared the dressing-room as players, while Owen had his father as a coach at Saracens, England and the Lions before he joined up with Ireland as defence coach in 2016.
Since then, they have faced off four times and they've won two each.
"When was that? I can't remember," he said of the first time they met in 2017. "Honestly, it's been so many times now. I can't even remember how it felt.
"You know what, there is an element of... I am proud of the situation, I am as far as a father and him as a son, I am proud of how it is handled because it is one of the utmost respect, but of professionalism, first and foremost."
For those involved, it's easy to get to grips with the dynamic. Not so for the rest of the household.
"I know, it's weird, isn't it?" he said when the topic was first broached.
"Well, honestly, yeah, it is weird because I know it's weird for you guys (in the media) but it's certainly not weird for us because it's never been any different.
"It's as professional as it gets because that's all we've ever known with Owen being a professional and me being a professional coach. It's never been any different.
"The hardest part is certainly for Colleen. Yeah, 100%. And Owen's sisters, and the young fella Gabriel, it's weird for them.
"They've got unbelievably mixed emotions, I've no doubt, because they're only human, but I suppose how do they try and come to terms with it?
"I suppose they think that, they hope that, both sides do well.
"And that's not going to happen, is it? So it's a difficult one for them."
They will, he says, be in touch between now and the game.
"Probably, yeah. What about, I don't know. It certainly won't be about our tactics, and it certainly won't be about his, so..."
Last week, the build-up to the Calcutta Cup match between Scotland and England was dominated by over-inflated hype, with the word 'hate' featuring more prominently than normal. It is not a road Farrell wishes to go down.
"No. No, 100%. The game's tough enough, and there's a mutual respect between the players, and the coaches as well. So I wouldn't even go down that road.
"We've family on both sides and we're unbelievably proud of that.
"I speak to all the Irish fans who love going to Twickenham and they tell me that everyone is unbelievably friendly, and that's why they keep coming back for a great day out."
For all of the pride he feels, the competitor in Farrell is targeting a win at his old stomping ground next weekend.
He's respectful of an opposition he knows more than most, but believes Ireland are gearing up for a performance.
"I'm as confident as you can be going to Twickenham," he said. "We know the task in hand. We know what awaits you when you get there.
"We know that England are pretty proud to play at home like we are to play at the Aviva. We feel like we're in a decent place. We're looking forward to next week. We've had a good couple of days here. I'm sure the lads are relishing coming into camp on Monday night, looking for a big week ahead. We'll need to be like that."
Anthony Watson's participation in the remainder of England's Guinness Six Nations campaign is uncertain after he was ruled out of the round three fixture against Ireland.
Watson was due to start the opener against France but was withdrawn on the eve of the team announcement because of a calf problem.
The Bath wing was then ruled out of last Saturday's Calcutta Cup victory over Scotland and Jones has revealed he will miss at least one more game.