Woe betide any Manchester United player who reports late now that Erik ten Hag has been confirmed as the new boss at Old Trafford.
The Dutch coach is a stickler for punctuality. If a press conference is scheduled to begin at midday, the door will open at 11.59 and the first question asked will be 12 on the dot.
If a line of questioning becomes too persistent - and the Dutch press have discovered this recently in tetchy exchanges over his new job - then Ten Hag will raise his sleeve and glance at his watch.
That is the signal for the press officer to wrap things up. No more questions.
Since it became clear Ten Hag was United's favoured candidate - the man a declining club hope will have a similarly transformative impact as a certain Eric Cantona three decades ago - journalists have repeatedly tried to get him to talk about it. But to no avail.
On Friday, ahead of the Dutch Cup final against PSV Eindhoven, his reply was brusque: 'Yeah, you can keep trying to ask me about this, but I am here to talk about Ajax.'
A follow up question received similarly short shrift: 'I will repeat myself one more time. Do you have any questions about the cup final? About Ajax?'
And on Sunday night, after his Ajax side were beaten 2-1 by PSV, this taboo topic was broached again.
'Now we should close this press conference,' came the curt response. This was given in English, which is more than passable.
This Ten Hag tetchiness of late has spilled over into other subjects. Andre Onana is one.
The Cameroon goalkeeper had started to play regularly again following his nine-month doping ban.
However, Ten Hag wasn't impressed with his fitness levels or performances and dropped him from his squad entirely for Sunday's final. Onana said previously he 'didn't care' about the criticism.
Despite the reasons being obvious, Ten Hag had suggested that Onana was injured and kept up the pretence in a TV interview on ESPN. It went like this:
Ten Hag: 'Onana is injured.'
Interviewer: 'Do you believe he is injured?'
Ten Hag: 'I just told you he is injured.'
Interviewer: 'Isn't he just sick of it?'
Ten Hag: 'He is injured.'
This final response was accompanied by a firm hand to the interviewer's shoulder. No more questions.
He also bristled in the same interview when asked why he dropped 33-goal top scorer Sebastien Haller for 20-year-old Brian Brobbey.
Interviewer: 'I assume you do this so that you have more depth up front?'
Ten Hag: 'Why do you always answer the question within your question?'
As it happened, Ten Hag's decision to bench Haller backfired and Ajax were unable to recover from a one-two PSV punch of two goals in three minutes early in the second-half.
When he finally introduced Haller in the 72nd minute it was too little, too late.
There was a growing view in Holland that he should have just talked about United to end the constant questioning he clearly hated and soothed relations with the press.
That would have allowed matters to move forward and Ajax to concentrate on the remaining five matches of the Eredivisie season, where they lead PSV by four points in the title race.
But we should not discount the reality that Ten Hag is so focused on delivering another title to Ajax that he doesn't want the United issue to become a distraction. He also doesn't want to disrespect the club he has managed since December 2017.
Ten Hag's reputation as a control freak isn't accidental. He is a man who spends hours in his tracksuit at the training ground meticulously analysing every aspect of his team's upcoming opponents.
Although Ajax had already played PSV three times this season, Ten Hag spent the build-up to the final poring over them once again. Nothing was left to chance.
This continues through the match itself. A 'brains trust' of four technicians sat in the press box to gain a wide-angle view of the action as it unfolded.
One carried a sheaf of papers detailing set-piece routines and communicated with the bench via a radio headset.
But there are some things even Ten Hag and his boffins cannot control. As he said afterwards: 'There is only one club that should have lifted the trophy today, and that's Ajax. But we made two individual mistakes in a matter of minutes.'
Through it all, Ten Hag cut a mild-mannered figure on the touchline.
Old Trafford will not be witnessing any Jose Mourinho or Louis van Gaal-style histrionics, nor the frenetic arm windmilling of Ten Hag's mentor at Bayern Munich, Pep Guardiola.
When Ryan Gravenberch opened the scoring, he reacted with a little fist pump but that was the only show of emotion. He was soon back to being statuesque.
Officials in the Premier League can expect an icy glare if decisions go against United, however. Ten Hag might have to be careful, especially in a second language.
After the final, he claimed Ajax, who had two goals disallowed by the most fractional of VAR decisions, 'played against more than 11 men.'
First interactions with the English press will be fascinating. Ten Hag will quickly appreciate there will be infinitely more demands on his time from the world's media when he arrives at United and he probably won't be comfortable with it.
A man so meticulous should be under no illusions as to the size of United. But if he is, a pre-season tour that sees them play Liverpool in Bangkok and then two games at the 100,000-capacity Melbourne Cricket Ground will shatter them.
This is said with all due respect to Ajax, of course.
His strong work ethic reflects his upbringing in the rural east of the Netherlands. Ten Hag has a strong provincial accent and this was held against him when he first arrived in Amsterdam.
But success has won over the doubters even if he occasionally still attracts mockery for an inelegant use of English and hoarse voice.
An interview he did on Sky Sport Italia when Ajax played Roma in last season's Europa League went viral.
'I like Italy, I like the culture, I like the people, I like the country. It is fantastic also how they expire football. So, yeah, really good country,' he said.
But Ten Hag's English has improved with lessons even if he may persist starting each answer with 'ja' or 'nee' as he does now.
Meticulousness and success also creates authority. United's players can expect him to impose rules. Even as a youth team coach starting out, he cut short the players' time off and punished anyone who reported back late.
But he does fully immerse himself with his playing squad, sending them video clips of upcoming opponents and even advising them which newspaper articles to read.
It could be a rude shock for a United dressing room that has been coasting for far too long now.
Certain players won't respond well to a hardline coach who makes no exceptions but equally Ten Hag has never encountered a dressing room full of such lavishly-paid stars.
He is also known to utilise his full squad, giving opportunities to players who perform well in that week's training sessions. As Haller discovered, nobody is immune to being dropped.
They'll have to buy into his philosophy as well. The whole Ajax team moves up and down the field in a kind of fluid motion, a post-modern version of Total Football.
When they attack, every outfield player must push forward into the opposition half. The wing-backs are expected to get right forward.
But when the opposition comes forward, everyone - without exception - must track back. Hard-running and constant movement is required - and we all know how United's pampered players refused to buy into Ralf Rangnick's heavy pressing.
It is hoped United's players will come to respect Ten Hag's work ethic - his family remained in the Twente region and he only makes the four-hour round trip from Amsterdam on his days off.
What's interesting is that Ten Hag never had to be this devoted. He comes from a very wealthy family who own real estate and financial firms.
But playing football always fascinated the former defender and coaching became a natural post-career path. He was especially engaged when coach of Bayern Munich's second team and enjoyed sharing ideas with Guardiola.
Because Ten Hag was responsible for producing players schooled in Guardiola's way for the first team, a lot of the Spaniard's methods rubbed off.
While he won't be intimidated by the United job, Ten Hag will make clear that his best contribution to the Old Trafford rebuild will be in a tracksuit on the training ground.
John Murtough, the director of football, can take care of transfer dealings while the manager does what he does best.
All United's players have to do is buy into his vision. And turn up on time.