(CNN) -- McLaren's Lewis Hamilton set the pace in Friday practice ahead of his home British Grand Prix, on a day which saw heavy rain batter the Silverstone track and left organizers with a big headache.
Hamilton's lap on one minute 56.345 seconds in the afternoon session was 0.129 seconds faster than that of Sauber's Kamui Kobayashi, after Romain Grosjean of Lotus went fastest in the morning.
"I had some fun out there today," the 27-year-old said in a McLaren statement. "I got to do a good few laps too, which was good, because I was concerned that the fans wouldn't get to see much action.
"There were so many of them out there today. I can't remember seeing so many people at a racetrack on a Friday before -- it was incredible. British Formula One fans are the best in the world.
"I would like to have gone out and done even more laps -- but we simply didn't have enough tires to do that. Perhaps that's something we can look at for the future."
But those fans were told to stay away from the famous circuit Saturday if they had been planning to use public car parks.
The downpours have left these areas flooded and Silverstone managing director Richard Phillips gave this warning.
"Tomorrow there will be 20,000 to 30,000 people we won't be able to properly cater for.
"It's going to cost us a lot of money.
"I unreservedly apologize to people. I feel very responsible for it, this is something I've been very proud of over the years and I almost could cry now."
Over 40 millimeters of rain has fallen in 12 hours and made conditions treacherous for the drivers, with Bruno Senna smashing into the wall after losing control of his Williams midway through the second session.
Two-time world champion and current title leader Fernando Alonso also lost his front wing after clipping the barriers.
"Unfortunately we didn't have a very productive day in the end," the 28-year-old Senna said in a Williams press release.
"The weather was poor weather with puddles on the track during second practice. On my second run, I aquaplaned on some deep water at the high speed Becketts section of the track and from that point I was a passenger until the car hit the wall.
"It was quite a heavy accident but I am ok. There is a lot of damage to the car but the Williams team will, I'm sure, do a great job of getting it back into shape for tomorrow (Saturday)."
Red Bull's reigning world champion Sebastian Vettel, currently fourth in the 2012 standings, bemoaned the wet conditions.
Regulations limiting the number of wet and intermediate tires teams can use combined with the weather meant most of the action was restricted to the second half of the afternoon session.
"If there's too much standing water on track we can't go out, as we aquaplane pretty quickly," Vettel, who finished second in last year's race, told the sport's official website.
"I think Senna went off and it shows how quickly it can happen. It's a real shame for the fans sitting in the grandstands waiting for the cars to come out. I feel for them.
"We got in a bit of running in the end, but for us it's not so useful, as you can't really try anything in these conditions. I think weather will be the most important factor in determining the rest of the weekend."
The teams will return to the track for practice and final qualifying Saturday ahead of Sunday's ninth grand prix of the year.