A last-gasp flying lap from Johnny Cecotto on super soft tyres gave the Addax driver first place at the end of GP2 free practice in Monte Carlo.
Cecotto and championship leader Davide Valsecchi jumped to first and second just after yellow flags for an incident involving Cecotto's team-mate Josef Kral were removed.
Although a massive 0.670 seconds separated Cecotto's 1m22.075s benchmark from Valsecchi's second-placed time, the DAMS driver was using soft tyres rather than super softs like his rival.
Racing Engineering's Fabio Leimer had looked set to stay on top with his 1m22.750s as the yellow flags flew in the final minute, before swift work by the marshals allowed Cecotto and Valsecchi to stay on the accelerator on their last laps and demote Leimer to third.
Giedo van der Garde had led the way for Caterham for much of the session, but spun and tapped the barriers at Rascasse with four minutes to go, ending his morning. The Dutchman was then pushed back to fourth.
Jolyon Palmer (iSport) and early pacesetter Luiz Razia (Arden) completed the top six, ahead of Trident's Stefano Coletti, Carlin's Max Chilton (who also held first for a spell), Leimer's team-mate Nathanael Berthon, and Kral.
The latter's incident came when he spun out of the second part of the Swimming Pool and brushed the barriers.
Also in trouble were Lazarus man Giancarlo Serenelli, who spun and stalled at Rascasse, and Lotus's Esteban Gutierrez, who crashed at Sainte Devote before he could set a representative time.