Daniel Ricciardo set a new Formula 1 track record around the streets of Monaco as he led a Red Bull 1-2 during Thursday’s opening practice session.
Last year’s pole position time was beaten by Ricciardo as teams evaluated Pirelli’s new-for-2018 Hypersoft tyres in warm and sunny conditions in the 90-minute session.
Ricciardo’s team-mate Max Verstappen and Mercedes’ Lewis Hamilton had exchanged honours atop the timesheets, while Ricciardo was skewered by traffic in the final sector.
Ricciardo, though, re-emerged to move to within a tenth of his team-mate before overhauling him altogether, winding up on a 1:12.126.
The Australian's time was half-a-tenth up on Kimi Raikkonen’s pole-winning effort from 12 months ago.
Monaco GP: FP1 result in full
Verstappen finished 0.154s behind Ricciardo and is under investigation for allegedly re-joining the circuit in an unsafe manner, having locked up heavily into Sainte Devote.
Verstappen reversed onto the circuit and the pursuing Sebastian Vettel opted to cut the corner in order to avoid the Dutchman’s errant RB14.
Erstwhile pacesetter Hamilton finished third, behind the two Red Bulls, his best effort 0.354s down on Ricciardo’s lap.
Ferrari, which took a 1-2 last year in both qualifying and the race, was a low-key fourth and fifth, with Vettel and Raikkonen nine-tenths adrift of Ricciardo.
Renault’s Carlos Sainz Jr. broke the hegemony of the usual leading six as he crept ahead of Mercedes’ Valtteri Bottas to grab sixth spot.
Force India’s Sergio Perez was eighth, as Romain Grosjean flirted with the barriers at Tabac and Piscine and had to spend time in the garage while Haas worked on a floor issue, and ultimately finished ninth overall.
Sergey Sirotkin damaged the right-rear of his Williams FW41 when he brushed against the pit wall early on but recovered to the pits and returned to action to round out the top 10.
Force India's Esteban Ocon was 11th while Renault's Nico Hulkenberg split Toro Rosso pair Brendon Hartley and Pierre Gasly, the Honda-powered drivers setting their best times on Ultrasofts.
McLaren had a lacklustre session; Stoffel Vandoorne could set only the 15th-best time while Fernando Alonso, who missed last year’s event, was 17th, having spent most of the session in the garage while a suspected brake-by-wire system issue was assessed.
Home representative Charles Leclerc took 16th, with Lance Stroll, Marcus Ericsson and Kevin Magnussen at the foot of the timesheets.
Magnussen managed only a handful of laps before Haas detected a suspected injector issue in his VF-18, consigning him to the garage for the bulk of the session.
Thursday’s second 90-minute practice session is scheduled for 15:00.
