Lucas Auer set the fastest time during the 80 minutes of free practice ahead of this weekend's Formula 3 European Championship round at Brands Hatch.
The Austrian, who has never raced at Brands but learned the 1.2-mile Indy circuit a couple of months ago in a test in a Formula Renault BARC car, edged out Prema Powerteam Dallara-Mercedes team-mate Raffaele Marciello by 0.049 seconds.
Championship leader Marciello was narrowly ahead of the Mucke Motorsport Dallara-Mercedes of Felix Rosenqvist, who headed the first 40-minute session.
An improvement on the very last lap meant that Mans Grenhagen moved up to fourth, just behind fellow Swede Rosenqvist, in his Van Amersfoort Racing Dallara-Volkswagen.
Felix Serralles (Fortec Motorsport Dallara-Mercedes) and Jordan King (Carlin Dallara-VW) rounded out the top six.
The most significant incident occurred with two minutes remaining in the first session, when Alex Lynn - second fastest at the time - spun at McLaren and gently nosed his Prema car into the barriers at Clearways.
The Englishman missed the first 12 minutes of the second session, but went seventh fastest, just 0.002s behind fifth fastest Serralles.
Tom Blomqvist, Dennis van de Laar and Michael Lewis completed the top 10. Of the other UK drivers, Harry Tincknell was 11th, Josh Hill 12th, Will Buller 13th and Jann Mardenborough - the last man within half a second of the fastest time - 18th.
Qualifying takes place later this afternoon, with the field split into two groups - odd and even numbers - for their two sessions owing to traffic concerns arising from a 29-car field on a 41-second lap.
Combined practice times:
Pos Driver Team/Car Time Gap
1. Lucas Auer Prema Dallara-Merc 41.276s
2. Raffaele Marciello Prema Dallara-Merc 41.325s + 0.049s
3. Felix Rosenqvist Mucke Dallara-Merc 41.348s + 0.072s
4. Mans Grenhagen Van Amersfoort Dallara-VW 41.450s + 0.174s
5. Felix Serralles Fortec Dallara-Merc 41.468s + 0.192s
6. Jordan King Carlin Dallara-VW 41.469s + 0.193s
7. Alex Lynn Prema Dallara-Merc 41.470s + 0.194s
8. Tom Blomqvist Eurointernational Dallara-Merc 41.478s + 0.202s
9. Dennis van de Laar Van Amersfoort Dallara-VW 41.532s + 0.256s
10. Michael Lewis Mucke Dallara-Merc 41.560s + 0.284s
11. Harry Tincknell Carlin Dallara-VW 41.596s + 0.320s
12. Josh Hill Fortec Dallara-Merc 41.601s + 0.325s
13. Will Buller T-Sport Dallara-Nissan 41.603s + 0.327s
14. Sven Muller Ma-con Dallara-VW 41.613s + 0.337s
15. Lucas Wolf URD Dallara-Merc 41.654s + 0.378s
16. Antonio Giovinazzi Double R Dallara-Merc 41.672s + 0.396s
17. Daniil Kvyat Carlin Dallara-VW 41.683s + 0.407s
18. Jann Mardenborough Carlin Dallara-VW 41.723s + 0.447s
19. Nicholas Latifi Carlin Dallara-VW 41.837s + 0.561s
20. Pipo Derani Fortec Dallara-Merc 41.874s + 0.615s
21. Eddie Cheever Prema Dallara-Merc 41.891s + 0.686s
22. Roy Nissany Mucke Dallara-Merc 41.962s + 0.748s
23. Spike Goddard T-Sport Dallara-Nissan 42.024s + 0.790s
24. Mitchell Gilbert Mucke Dallara-Merc 42.066s + 0.916s
25. Andre Rudersdorf Ma-con Dallara-VW 42.192s + 1.740s
26. Sean Gelael Double R Dallara-Merc 42.385s + 1.109s
27. Tatiana Calderon Double R Dallara-Merc 42.646s + 1.370s
28. Sandro Zeller Zeller Dallara-Merc 42.755s + 1.479s
29. Michela Cerruti Romeo Ferraris Dallara-Merc 43.815s + 2.539s