Norris makes it double top in McLaren 1-2 at Silverstone practice
Showing no ill-effects after his controversial collision with Max Verstappen at last Sunday's Austrian Grand Prix, the 24-year-old Britain thrilled his home fans by topping the times in both free practice sessions.
His best lap in one minute and 26.549 carried him 0.331 seconds clear of Piastri in a convincing McLaren one-two.
Behind the two McLarens, Red Bull's Sergio Perez enjoyed a welcome return to form by finishing third ahead of Nico Hulkenberg of Haas, Ferrari's Charles Leclerc and seven-time champion Lewis Hamilton of Mercedes.
"The track is fine," said Hamilton, a record eight-time winner of his home event. "I'm just slow."
Series leader and three-time champion Max Verstappen was seventh in the second Red Bull ahead of Carlos Sainz in the second Ferrari, Lance Stroll of Aston Martin and George Russell in the second Mercedes.
On a cool, grey summer's day in central England, the session began with Yuki Tsunoda clocking the opening lap time before the Ferrari duo of Leclerc and Sainz took over. It was not for long, however, as Verstappen and Norris replaced them.
Taking softs, Verstappen trimmed his time to 1:27.233 -– eight-tenths clear of all his rivals –- to show the potential pace of his Red Bull this weekend, but Russell, on mediums, closed within three-tenths to show that Mercedes remained contenders.
Alonso then threatened before Leclerc went top only to be outpaced immediately by Hulkenberg in his Haas before Piastri gained the initiative.
By the midway point in the session, black clouds were threatening as Norris jumped three-tenths clear of his McLaren team-mate in 1:26.549, the duo showing a clean pair of heels to their rivals as rain fell intermittently.
"When the rain hits, it could be quite heavy and quite quickly," McLaren informed Norris. "We'll take no risks."
Soon after this, Norris drifted his car around at Nuffield as if to show his control and sense of fun before the rain swept across the former war-time airfield and most drivers headed into the pits.