Romain Grosjean showed the rest of the field how best to deal with the infamous Monaco traffic by claiming the top spot in this morning's free practice session, just ahead of Lucas di Grassi and Luca Filippi.

The Frenchman ran on a different schedule to most of his closest rivals to set a best lap time of 1:21.267, almost two tenths faster than his nearest rival 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 Filippi who was soon sitting on top 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 stop.

But it 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 coming out of St Devote after passing Michael Herck the session was red flagged, and Grosjean's competitors were forced to wait until this afternoon's qualifying session to prove that they've got more in reserve.