Lewis Hamilton will defy his own Mercedes team and Formula One's new owners by missing Wednesday's showpiece demonstration on the streets of London.
The triple world champion announced on social media that he would not take part in the event four days before the British Grand Prix at Silverstone.
Hamilton's unilateral decision casts doubt on his long-term future at Mercedes - raising the question of whether some underlying tension between star driver and team is at the root of his non-appearance.
On the day Silverstone confirmed they were pulling out of their contract to host the British Grand Prix from 2019, Hamilton tweeted: 'To my loving fans, I can't wait to see you at Silverstone. Until then, I'm away on a two-day break. God bless you all. Love, Lewis.'
The rest of a stellar cast will show up for an occasion close to the hearts of owners Liberty Media, but Hamilton's love is all an anticipated 250,000-plus crowd will get from him as F1 cars are driven from Trafalgar Square along Whitehall.
It is understood that Liberty only learned of Hamilton's defiant stand from his social media yesterday afternoon, though Mercedes say he made his position known during the last race in Austria.
Several of the owners' management team spent the day in central London preparing for the multi-million pound promotion, and they were said to be surprised and disappointed by the news.
They were all the more shocked given that the drivers were briefed about the day's itinerary, the specifics of which have been kept a secret until the last moment.
Mercedes, like all the other teams, bought into the idea and lent enthusiastic support.
So much so that Mercedes' reigning, though retired, world champion Nico Rosberg is flying out to perform. Renault's Jolyon Palmer, the only British driver in F1 other than Hamilton, will take part and 2009 champion Jenson Button is equally committed.
After a run of so-so recent results that has left Hamilton 20 points off leader Sebastian Vettel of Ferrari, the temperature is hotting up within Mercedes.
Meanwhile, Silverstone's decision to trigger an escape clause in their contract to host the British Grand Prix - as reported here on Tuesday - has been criticised by Red Bull team principal Christian Horner.
The Northamptonshire circuit's announcement was also denounced by their negotiating partners, Liberty, who said they 'deeply regret that Silverstone have chosen to use this week to posture and position'.
Horner said: 'Silverstone signed a contract knowing what they were entering into. They either should not have signed it in the first place, or they got their maths wrong. There has been serious mismanagement.'
'It is hard to imagine they lose money putting 140,000 people in there on race day.' Silverstone and Liberty are committed to renegotiating a deal.