Kevin Magnussen ensured McLaren topped the first day of Formula 1's Silverstone young driver test.
The Dane had not been a factor at the head of the time sheets until the final 20 minutes, when he bolted on medium tires and set a 1m33.602s that would prove unmatched for the remainder of the session.
While the afternoon did not yield massive improvements, positions changed hands multiple times as drivers found incremental gains. Among them was Paul di Resta, the first of this year's regular drivers to run on Pirelli's new tires.
The Scot took over from morning pacesetter James Calado in the Force India and immediately improved upon the latter's benchmark. He was temporarily demoted to second by Red Bull's Antonio Felix da Costa, who was given a full day of running following a late reshuffle that means Mark Webber will no longer test.
Di Resta regained the advantage after a run on Pirelli's hard compound, but his 1m33.774s was eclipsed by Magnussen late in the afternoon. Da Costa ended the session third, ahead of Calado and Williams's Daniel Juncadella. The Spaniard's morning was disrupted for bodywork repairs, and while a clear afternoon lifted his total to 55 laps, he was still some way short of Magnussen's tally of 100.
Johnny Cecotto Jr. (Toro Rosso) edged Sauber reserve Robin Frijns in the fight for sixth after his own late improvement. Frijns set his best time early in the afternoon, putting him fourth at the time, but dropped back as Magnussen and then Cecotto found time.
Nicolas Prost (Lotus), Davide Rigon (Ferrari) and Alexander Rossi (Caterham) rounded out the top 10. Rossi's day was brought to a close 30 minutes before time due to a mechanical issue.
Marussia locked out the final two spots through Tio Ellinas and Max Chilton, both of whom were more than three seconds off the pace.
Chilton's afternoon was severely disrupted by an ECU issue that meant he was only able to get out in the final hour, and only able to complete 25 laps in total, the majority of which he devoted to a late long run.
Pos Driver Team Time Gap Laps
1. Kevin Magnussen McLaren 1m33.602s 100
2. Paul di Resta Force India 1m33.774s +0.172s 58
3. Antonio Felix da Costa Red Bull 1m33.821s +0.219s 82
4. James Calado Force India 1m33.986s +0.384s 27
5. Daniel Juncadella Williams 1m34.098s +0.496s 55
6. Johnny Cecotto Toro Rosso 1m34.193s +0.591s 75
7. Robin Frijns Sauber 1m34.236s +0.634s 72
8. Nicolas Prost Lotus 1m34.810s +1.208s 72
9. Davide Rigon Ferrari 1m34.874s +1.272s 76
10. Alexander Rossi Caterham 1m35.651s +2.049s 69
11. Tio Ellinas Marussia 1m36.676s +3.074s 36
12. Max Chilton Marussia 1m38.347s +4.745s 27