Having claimed the upper hand after the opening round in Barcelona two weeks ago, Romain Grosjean showed the rest of the GP2 Series field how best to deal with the famous Monaco traffic by claiming top spot in the sole free practice session in the Principality.

The Frenchman ran a different schedule to most of his closest rivals to set a best lap of 1min 21.267secs, almost two tenths faster than nearest rival Lucas di Grassi, who was changing tyres as Grosjean set a string of quick laps halfway through the session.

The session opened under clear blue skies, with Andreas Zuber and Alberto Valerio swapping fastest times early in the session, but it was Luca Filippi who soon took control of the timesheets, while Grosjean was caught out in heavy traffic at Rascasse, tapping the rear of an almost stationary Davide Valsecchi and prompting an early pit-stop.

That, however, proved to be an inspired move. Grosjean, di Grassi and Filippi were soon swapping fastest laps, but it was the Frenchman who was able to take advantage when his rivals were forced to pit for fresh tyres.

In the closing minutes of the session it was clear that a challenge was going to be made to the top time, but when Valerio caught the wall just out of Ste Devote after passing Michael Herck the session was red flagged, and Grosjean's competitors were forced to wait until the afternoon qualifying session to prove that they've got more in reserve.

Grosjean's Barwa Addax team-mate Vitaly Petrov and ART's experienced Pastor Maldonado rounded out the top five, ahead of Zuber, Javi Villa, Karun Chandhok, Dani Clos and Alvaro Parente. DAMS duo Kamui Kobayashi and Jerome d'Ambrosio were lower down the order than most would have imagined, in 17th and eleventh respectively.