The race is part of the Government's Events Research Programme (ERP), meaning masks are not mandatory.
However, on the day the UK announced over 50,000 new Covid cases, 90,000 watched on at the famous racetrack for free practice and qualifying.
"It was so nice to see everyone today,' wrote Hamilton. "So refreshing to see people and the energy already is so uplifting.
"Can I please ask you to wear your masks, be safe. I know of people getting Covid and being ill even with double jabs. So please please stay safe this weekend.
"Wearing a mask is a small sacrifice to stay healthy and keep others around us healthy. With love."
The capacity crowd had to provide proof of full vaccination or a negative lateral flow test taken within 48 hours of arrival.