Michael Schumacher started his 20th anniversary celebration weekend in appropriate style by leading the opening practice session at Spa, as Formula 1 resumed after its summer break, but the position was somewhat deceptive as only the Mercedes managed laps in the dry.
A heavy shower hit the Belgian venue just 10 minutes into the session, and track conditions never improved enough to allow further running on slicks.
Mercedes duo Schumacher and Nico Rosberg had set flying laps by that time, and their respective 1m54.355s and 1m54.829s would stand as the morning's fastest times by a vast margin - a suitable, if unusual, way to Schumacher to kick off the weekend that marks 20 years since his F1 debut for Jordan.
The track was completely empty for 25 minutes after the shower, before championship leader Sebastian Vettel set off for an exploratory lap. He was soon joined by Lewis Hamilton, although a violent twitch for the McLaren at Blanchimont showed that the Briton's choice of intermediate tyres was optimistic at the time.
Force India's Adrian Sutil was first to try a flying lap on wets, lapping 21s off the Mercedes' earlier pace. By the end it was Jenson Button who managed the fastest rain time for McLaren, with a lap of 2m02.740s - 8.3s away from Schumacher's mark - on intermediates in the closing minutes.
Vettel (Red Bull) grabbed fourth with a similar last-gasp run, followed by Hamilton. Sutil remained a frontrunner and was sixth, ahead of Toro Rosso's Jaime Alguersuari, Felipe Massa's Ferrari and Kamui Kobayashi (Sauber)
Bruno Senna's return to a race seat with Renault did not begin well, as he spun into the tyres at the nameless Turn 9 left-hander with half an hour to go. Paul di Resta would later crash his Force India at the same place, and although the Scot's accident was less damaging, it required a seven-minute red flag stoppage as the crane needed to clear the car away was already engaged with Senna's Renault.
Pos Driver Team/Car Time Gap Laps
1. Michael Schumacher Mercedes 1m54.355s 13
2. Nico Rosberg Mercedes 1m54.829s + 0.474s 15
3. Jenson Button McLaren-Mercedes 2m02.740s + 8.385s 8
4. Sebastian Vettel Red Bull-Renault 2m03.752s + 9.397s 10
5. Lewis Hamilton McLaren-Mercedes 2m04.301s + 9.946s 7
6. Adrian Sutil Force India-Mercedes 2m04.663s + 10.308s 18
7. Felipe Massa Ferrari 2m04.728s + 10.373s 10
8. Rubens Barrichello Williams-Cosworth 2m05.391s + 11.036s 12
9. Jaime Alguersuari Toro Rosso-Ferrari 2m06.583s + 12.228s 16
10. Kamui Kobayashi Sauber-Ferrari 2m06.886s + 12.531s 15
11. Fernando Alonso Ferrari 2m07.055s + 12.700s 12
12. Sergio Perez Sauber-Ferrari 2m07.481s + 13.126s 15
13. Jarno Trulli Lotus-Renault 2m08.233s + 13.878s 14
14. Sebastien Buemi Toro Rosso-Ferrari 2m08.239s + 13.884s 14
15. Pastor Maldonado Williams-Cosworth 2m08.918s + 14.563s 10
16. Mark Webber Red Bull-Renault 2m09.792s + 15.437s 8
17. Timo Glock Virgin-Cosworth 2m12.278s + 17.923s 13
18. Tonio Liuzzi HRT-Cosworth 2m12.389s + 18.034s 10
19. Jerome D'Ambrosio Virgin-Cosworth 2m12.772s + 18.417s 13
20. Paul di Resta Force India-Mercedes 2m13.058s + 18.703s 8
21. Karun Chandhok Lotus-Renault 2m13.090s + 18.735s 11
22. Vitaly Petrov Renault 2m13.601s + 19.246s 10
23. Bruno Senna Renault 2m14.340s + 19.985s 7
24. Daniel Ricciardo HRT-Cosworth 2m14.933s + 20.578s 11