On Sunday we have round 12 of this year's F1 Championship at Spa in Belgium. The BBC's Murray Walker, who has been covering motor racing since the late 1940s, reckons there are two drivers worth following in Sunday's race.

In his video preview, which you can see here, he says: "This is the race above any other that I look forward to every season. Put simply, the circuit is without doubt the finest in the world and represents one of the most unpredictable and exciting races year in, year out.

"But for my money - and be warned I have been known to be wrong - it comes down to two teams and two drivers."

Walker says it all depends on the weather. If it's dry and sunny he reckons Brawn's Jenson Button is the driver to follow. But if, as often happens at Spa, we get a sudden downpour and the track turns wet, he says backing Lewis Hamilton is the best play.

According to the weather forecast, which you can see here, there is no rain forecast between now and Sunday. On Sunday itself it should be around 70 degrees and be partly cloudy - but no rain.

This suggests that at a best-priced 9/1 with Bwin Jenson Button is the driver to back to win on Sunday. Alternatively, if you're a betting exchange player, laying Sebastian Vetel at 4.1 on Betfair could also make you a few quid.