Aston Martin's Lance Stroll collected a one-place grid drop for causing a collision with Ferrari's home hero and pacesetter Charles Leclerc in first practice for the Monaco Formula 1 Grand Prix.
Leclerc, last year's winner from pole position, broke his front wing in the incident but, after a brief red flag period, ended Friday's opening session on top around the twisty harbourside street circuit.
His time of 1:11.964 was 0.163 seconds quicker than Red Bull's four-time world champion Max Verstappen, winner last Sunday in Imola.
McLaren's Lando Norris was third with championship-leading teammate Oscar Piastri fifth, on the slower medium tyres, and behind Williams' Alex Albon.
Leclerc's teammate and seven-time world champion Lewis Hamilton was top early on but ended up ninth after going airborne over the kerbs at the swimming pool exit and possibly damaging his car's floor.
Mercedes' George Russell was sixth fastest with Williams' Carlos Sainz seventh and Alpine's Pierre Gasly eighth.
Aston Martin's double world champion Fernando Alonso completed the top 10, who were separated by just 0.7 of a second.
Leclerc and Stroll collided early on at the hairpin, with the session stopped to clear up debris and the Aston Martin suffering rear suspension damage and requiring a gearbox change.
Ferrari put a new front wing on Leclerc's car and sent him back out when the track re-opened.
Stewards found that Stroll had cut across Leclerc's path and was wholly to blame for the collision.
In his defence, Stroll said that although his team had warned him of Leclerc's approach, he did not hear the radio message.
Leclerc, on pole in three of the last four races in Monaco, had played down his team's chances on Thursday while hoping for a surprise.
Ferrari have lacked single-lap pace and struggled with slower corners this season but Monaco, the slowest track of all, offers the chance to set up the car without having to compromise on straight-line speed.