Honda returned with McLaren in 2015, but for four seasons struggled to develop its power unit as F1 returned to the turbo era, which ironically had brought championship success for Honda in the 80s. It won the constructors championship every year between 1984 ad 1991, with either McLaren or Williams.
In 2018, Honda partnered with Toro Rosso, and in 2019, Red Bull, the sister team to Toro Rosso, adopted the Honda engine with almost immediate success.
Max Verstappen won three races in 2019 in his Red Bull with a Honda engine and has won one race this season, but Honda has also had success with the Alpha Tauri team (formerly Toro Rosso), courtesy of Pierre Gasly's maiden grand prix win in the 2020 Italian GP.
Honda first entered F1 in 1964 and had its first success in 1965 with John Surtees in the Mexican GP. As an engine manufacturer, Honda has won six constructors championships and five drivers championships, but unless it can win with Red Bull next year, it won't be adding to its championship success.
"We have started to calculate how much it will cost with the future regulations," Honda's F1 managing director Masashi Yamamoto told Autosport.
"We have noticed that it's very tough for all the car manufacturers at the moment, because of the environment change for electrification. So, we are summing up the development cost and having discussions internally."
With Honda pulling the plug on its F1 activities because of the resources needed to shift to electrification in its road cars, Red Bull will need to find a new engine supplier after 2021. Marko has indicated they will research all possibilities. Asked if it was possible Red Bull itself could exit F1 at the end of the 2021 season, Marko has dismissed that possibility.
"We can cancel the contract annually, there is an option to exit at the end of each year," Marko explained. "But this is not our priority."
There will only be three engine options for Red Bull in 2022, Mercedes, Ferrari or Renault. Mercedes currently supplies Racing Point and Williams, and, in 2021, will also supply McLaren. It is therefore unlikely to supply a team that this year is its closest rival. Ferrari supply Haas and Alfa Romeo, but is struggling with its power unit, so is unlikely to help a team that is currently easily beating it.
The FIA regulations require a team with the least number of customers to supply a team without an engine supplier. That team is Renault, which next year is going solo, but of course there was a very public divorce at the end of 2018 between Red Bull and Renault, which had supplied the Austrian-owned, but England-based, team since 2007.
Red Bull and Renault won the drivers championship with Sebastian Vettel from 2010 to 2013 and also the constructors title for that period. But as Mercedes came to the fore in 2014 and has continued to dominate F1 ever since, there were rumblings of dissatisfaction in the Red Bull management about the Renault power unit, and the seeds of discontent were sown and grew to the point where the partnership became untenable.
Just how Red Bull will approach Renault and offer an olive branch, is anyone's guess.
Renault F1 team boss Cyril Abiteboul says he is yet to hear from Red Bull, which is not too surprising given there is a season and a half to go before Red Bull has no engine supplier.
"I can confirm there was absolutely no conversation to this point," Abiteboul told Autosport. "Being in the sport we are well aware of the regulation, and we have every intent to comply with the regulation and with our obligations.
"Obviously it's a bit more detailed - we need to be requested, and we have not been requested yet, and secondly there are very specific circumstances, including timing, for this to happen.
"I can't imagine Red Bull wouldn't have some plan in the background. Clearly, they must have been aware of this and Helmut and Christian [Horner] are full of moves and solutions. I don't expect we will be their Plan A," he added.
Dutch racing driver Tom Coronal has described Honda's decision as like dumping Red Bull at the altar.
"This is really shocking news," Coronal told Motorsport.com. "From Red Bull's perspective, they weren't even married yet. It was some kind of engagement, and they wanted to get married. Actually, at the altar, Honda now say 'no, we're not getting married'. That's kind of the feeling at Red Bull."
Coronal believes Honda will still be fully committed for 2021 and will have the budget already determined.
"Honda definitely won't disappear with their tail between their legs," he added. "They will always honour all the agreements."
But he does see the split as presenting Red Bull with a problem in retaining the services of Verstappen, who although he has a contract until 2023, is believed to have an escape clause in that contract.
"It's very simple, if Red Bull want to keep Max then they have to come up with a seriously good plan," Coronal says. "Max will always go with the best package, a package that can make him World Champion. That is really the only focus for Verstappen. That focus is not at all on earning money or on taking care of one's own name. No, the focus of the Verstappens is only one thing - becoming World Champion."
Just where Verstappen might go if he leaves Red Bull, is the big question, as Mercedes is the team that provides the best opportunity to be champion. Just ask Lewis Hamilton, who has already won five titles with Mercedes and is sitting pretty to make it six this season. Add those to his maiden championship in 2008 with McLaren and he is about to make it seven in total and equal Michael Schumacher's record.
The only one with a realistic chance to stop Hamilton is his teammate Valtteri Bottas. The latter won the Russian GP, thanks to Hamilton's controversial two five-second time penalties for practice starts in an undesignated area.
Controversial not because the penalties were questionable, but rather because Hamilton suggested the race stewards were out to stop him winning. He has since apologised for his outburst, presumably because the team feared he might incur a further penalty for bringing the sport into disrepute if he didn't.
Bottas trails Hamilton by 44 points in the championship, almost the equivalent of two race wins, with seven races remaining. Only more penalties, handing more victories to Bottas, can prevent Hamilton getting his seventh title. The team will set a record of seven consecutive constructors titles, regardless of whether Hamilton or Bottas win. Verstappen will know that being in a Mercedes is his best chance of a drivers championship, unless the regulation changes and budget cap for 2022 prove so dramatic that any of the 10 teams in the championship can win.
Even then, it is unlikely Mercedes will drop like a stone, and although Hamilton is yet to renew his contract with the team, that seems just a question of how much more money he can squeeze out of the German manufacturer, rather than Hamilton going elsewhere.
As long as Hamilton is a Mercedes driver, there is no way he will want Verstappen as a teammate, because some consider the ambitious, and still young, Dutchman to be better than Hamilton, or at least his equal.
Hamilton often argues he wants more competition, but not from his teammate. When Nico Rosberg beat him to the drivers championship in 2016 by five points, Hamilton did all he could in the season-ending race at Abu Dhabi to back Rosberg up into the opposition, knowing if he won the race (which he did), and Rosberg was third or worse, the seven-point difference would mean Hamilton would be champion.
Rosberg kept his nerve, and verve, and finished second to win the championship. You can be certain that Hamilton does not want a teammate equally as good, let alone better, than he is. Verstappen will have to hope that either Hamilton leaves Mercedes, or Red Bull secures an engine deal for 2022 that, with the new regulations, will give him a fighting chance. Right now, he is driving for second place, which is the first loser.
F1 returns to the Nurburgring this weekend for the inaugural Eifel Grand Prix.