An investigation into the legality of Lewis Hamilton's car at the Sao Paulo Grand Prix took a remarkable turn on Friday night when the stewards overseeing it adjourned their hearing and called on his title rival Max Verstappen to report to their office the following morning.
Hamilton could be excluded from the results of Friday's qualifying session and forced to start Saturday's sprint race from the pit lane if the drag reduction system (DRS) on his car is deemed illegal, but his Mercedes team appear to be putting up a fight.
On Friday evening, fan video emerged of Verstappen touching the rear wing and DRS assembly on Hamilton's car while it was in parc ferme after the qualifying session.
Several hours later, and once the stewards had adjourned their hearing at 9:55 pm local time, a summons was issued to Verstappen and his Red Bull team, citing an alleged breach of Article 2.5.1 of the FIA International Sporting Code.
The section of the International Sporting Code states that "inside the parc ferme, only the officials assigned may enter. No operation, checking, tuning or repair is allowed unless authorised by the same officials or by the applicable regulations".
Hamilton set the fastest time in qualifying for Saturday's sprint race, but during a post-qualifying inspection the operation of the DRS on his rear wing did not meet the requirements set under the regulations.
The DRS refers to a flap in the rear wing, which opens to reduce the car's drag on the straights and aid overtaking. Although its primary purpose is to improve racing, the DRS can be used freely in certain zones during a qualifying sessions to increase top speed.
Breaches of technical regulations have resulted in disqualifications from the results in the past, which in this case could see Hamilton forced to start Saturday's sprint race from the pit lane.
A disqualification would have huge ramifications on the championship. Hamilton trails Verstappen by 19 points with four races to go and already faces a five-place grid penalty for Sunday's event after Mercedes changed his engine ahead of the weekend.
If the wing is found to be in breach of the regulations, Hamilton faces the double whammy of starting from the pit-lane for Saturday's 24-lap sprint and then having a five-place penalty added to his finishing position in the sprint to determine his grid position on Sunday.
Were Verstappen to win the sprint race, the grand prix and score the bonus point for fastest lap, he would leave Sao Paulo with an additional 29 points on his tally.
FIA technical delegate Jo Bauer made the stewards aware of the alleged infringement on Friday evening, leading to a summons of a Mercedes team member at 7:15 pm local time.
"The uppermost rear wing element adjustable positions were checked on car number 44 for compliance with Article 3.6.3 of the 2021 Formula One Technical Regulations," Bauer wrote.
"The requirement for the minimum distance was fulfilled. But the requirement for the maximum of 85mm, when the DRS system is deployed and tested in accordance with TD/011-19, were [sic] not fulfilled."
The rear wing of Hamilton's car was removed by Mercedes under the supervision of Bauer on Saturday evening and will be impounded by the FIA until the investigation is complete.