Colombian Juan Pablo Montoya set the pace for Williams this morning in delayed final free practice for the Belgian Formula One Grand Prix.
Morning fog forced the cancellation of one of the two 45 minute scheduled practice sessions and prevented any action for two hours.
When the green light eventually allowed cars out, Montoya and German team mate Ralf Schumacher made an immediate impression on a high-speed circuit expected to favour their BMW-engined cars.
Ralf, using a new and modified chassis, looked to be fastest but Montoya pipped him just as the incident-free session came to a close with a time of one minute 47.494.
Ralf's best time was 1:47.768.
Brazilian Rubens Barrichello, chasing second place overall in a championship already won by Ferrari team mate Michael Schumacher, led the timesheets briefly but ended up fifth quickest.
The McLarens of Mika Hakkinen and David Coulthard, the Scot who managed only three laps on Friday before a heavy crash, were third and fourth quickest.
Jean Alesi beat Jarno Trulli into eleventh place in a disappointing session for the Jordan team.
Organisers had to repeatedly push back the start of practice due to low cloud, which shrouded the circuit in the wooded Ardennes hills.
The hour-long qualifying session is due to proceed as scheduled this afternoon.