Max Verstappen has topped opening practice for the British Grand Prix in a session that saw Alex Albon star.
While Verstappen headed a Red Bull one-two, a strong qualifying simulation lap from Albon saw the Williams driver third fastest.
His time was on par with that of Sergio Perez and 0.2s clear of Fernando Alonso behind him.
Red Bull sent Perez with an aero rake fitted to his car, the squad having introduced new brake ducts this weekend.
Although Ferrari is the only team without changes to its car this weekend, it coated the rear of Carlos Sainz's car with flo vis paint as it continued to evaluate recent tweaks.
There was neither on Lando Norris's McLaren despite the squad introducing the second batch of parts to his car.
Track grip was low, Max Verstappen complaining about it to his team while Nyck de Vries looped his Scuderia AlphaTauri at Luffield.
The rear wheels reached the gravel with the Dutchman lucky not to bog the car just 12 minutes into the session.
Despite running on hard tyres, Verstappen was the early pace-setter topping the opening minutes from Lance Stroll and the two Ferraris after 15 minutes.
That was despite describing conditions “like driving on ice,” with specific complaints of traction out of slow corners.
The early focus on car evaluation made the standings misleading; Alonso, for instance, had not completed a timed lap in the opening 25 minutes.
It was only halfway through the opening session that drivers and teams began to open the throttle.
Switching to the soft compound tyres for a qualifying simulation, Sainz went fastest with a 1:29.357s.
That left him 0.5s clear of Verstappen's earlier best, which had been logged on the hard compound rubber.
Not everyone immediately made the switch, Mercedes leaving Lewis Hamilton on the mediums.
Still, grip remained low on the 5.8km, while the seven-time champion complained of bouncing.
Following Sainz's effort, his Ferrari team-mate Charles Leclerc 0.06s slower to sit second fastest.
Like Hamilton, George Russell was also on the medium tyres though mustered a lap good enough for fourth, 0.622s away from the outright pace despite the tyre difference.
The Frenchman managed a 1:29.319s, 0.038s faster than Sainz.
A second lap from Leclerc saw the Ferrari driver go fastest shortly after, though by just 0.04s.
It highlighted the early potential of Alpine, which has a new front wing with a revised main plane and end plate for this event.
That is designed to offer better low-speed management of the airflow, the team outlined in a document published by the FIA.
Inside the final 15 minutes of the session, Verstappen headed out on a set of soft tyres.
He was immediately fastest, the 1:28.836s he managed proving 0.4s faster than Leclerc's time.
It was a composed lap, without brash aggression or hint that he was on the ragged edge.
Alex Albon surprised with a lap with eight minutes remaining, rising to second fastest for Williams just 0.25s away from Verstappen.
It left him 0.2s ahead of Alonso, who'd moved into third best, as all but Mercedes had run on the soft tyres.
Both Hamilton and Russell had moments, the former running wide and over the exit kerb at Stowe and the latter collecting a rear-end slide at Brooklands.
With three laps remaining, Verstappen underscored his pace with an even faster lap, extending his advantage to 0.448s over team-mate Perez.
McLaren ended the session with its cars in the top 10, Piastri's car suffering a hydraulics leak in the latter moments.
A question remains over Mercedes, which at no point ran the soft rubber, as both its cars ended proceedings outside the top 10 and Russell in particular struggling for grip.