You don't need to be an expert in human relationships to work out Mercedes boss Toto Wolff and Red Bull boss Christian Horner don't like each other very much.
While there's clearly a mutual respect between the two, Wolff and Horner have never shied away from taking jabs at the other in public. This has been the case once again over the past few weeks, with the pair exchanging shots very publicly during the Azerbaijan Grand Prix over Red Bull's controversial "flexi" wing.
But this beef stretches back years.
That's probably not surprising -- as head's of two of F1's most powerful teams, they often find themselves on opposing sides of the political issues which bubble away behind the scenes.
Add to that the on-track reality that one of them, Wolff, is in charge of the team that replaced the other's team as the dominant force in F1 in 2014. Things have an added dimension to them this year with Red Bull now leading both championships for the first time since 2013 and Mercedes seemingly being on the back foot.
Horner, especially, has never been one to shy away from confrontation. One of the most memorable parts of Netflix's Drive to Survive series was his awkward exchanges with former Renault boss Cyril Abiteboul.
A quick internet search with the right terms and you can find plenty of examples of Wolff or Horner telling the other to stop complaining about something. In 2015, Wolff scolded Horner for so publicly criticising engine supplier Renault and said he and Red Bull should just get their heads down and work harder to get back to the front. In 2016, Horner criticised Wolff for a phone call he made to Jos Verstappen to talk about his son Max's aggressive driving style, which was a contentious issue at the time.
In the years which have followed, in which Mercedes has enjoyed almost unprecedented success, Horner seems to have relished the opportunity to paint Wolff as someone who is scared of even the slightest threat to his team's dominance out in front.
When Mercedes blocked the reverse grid proposal that floated around ahead of the start of last year's delayed season, something Wolff likened to "a WWE gimmick", Horner accused the Austrian of being worried that it might threaten Lewis Hamilton's chances of a seventh world title.
The pair had also clashed before the pandemic, during pre-season testing in February, when Mercedes rolled out its innovative Dual Axis Steering (DAS) system.
While the rhetoric for the cameras was quite punchy, what happened behind closed doors was a bit less so. Horner and Red Bull lodged the protest against DAS ahead of the Austrian Grand Prix, something Wolff praised as being the right decision for F1 - there were fears a protest after the race would have put a dampener on the first event after the pandemic. The protest was rejected by the FIA.
While cooler heads seem to prevail behind closed doors both men like to control the narrative in the public discourse. Horner especially rarely misses an opportunity to poke the bear and his comments in Baku were effective in provoking a reaction.
Hamilton had been the first to comment on Red Bull's rear wing, which Horner said the seven-time world champion had been instructed to do by Wolff.
Horner went on full attack mode ahead of the sixth race of the year. In an interview with Sky Sports as footage was shown of Red Bull's wing appearing to flex at top speed, footage was also shown of Mercedes' front wing appearing to do similar.
To that, Horner said: "I think if I was Toto with the front wing he's got on his car, I'd keep my mouth shut."
The possibility of Mercedes lodging an official protest at Red Bull's rear wing lingered but never materialised at any point during the weekend.
But while Wolff and Mercedes did not take the issue any further with the FIA, Wolff was not willing to let Horner's statement go unchallenged.
Speaking in response to Horner's comments, Wolff told Sky Sports: "Christian is a bit of a windbag who wants to be on camera.
"It's easy to be punchy when you're on the top of the times sheets but you should be a little bit more modest."
It was a great soundbite which made for a superb headline.
The race which followed in Baku was remarkably dramatic and saw Mercedes leave without scoring a point. That prompted Wolff to say his team needed to improve across the board if it wants to beat Red Bull to the 2021 title.
Horner could not resist the opportunity to leave Baku with the final word.
When Wolff's comments were put to him, Horner said: ""I mean, a lot has been made about Toto's comments this weekend.
"He's never afraid to roast his team so publicly, which I disagree with. But that's his prerogative."
While the complaints over front and rear wings are likely to quieten down, the fact Red Bull and Mercedes are locked in a genuine championship battle this year means Wolff and Horner are going to have plenty of opportunities to keep this very public war of words alive until the end of the season.