Daniel Ricciardo set the fastest time on the second morning of this week's young driver test at Silverstone on Thursday as teams began shifting more focus on to tyre work.
The Australian was having a morning in his regular Toro Rosso car, prior to a move across to sister team Red Bull for the afternoon.
Operating to the strict tyre test programme mandated by Pirelli and the FIA, Ricciardo completed a series of runs on the new construction rubber that is being introduced from the Hungarian Grand Prix.
Having moved to the top of the timesheets early in the day as he evaluated the hard compound, Ricciardo stepped up to deliver his best effort of 1m32.972s during a spell of ever improving laps on the medium compound shortly before he handed over his car to Carlos Sainz Jr.
Antonio Felix da Costa, who was driving the Red Bull car that Ricciardo will take over this afternoon, ended the morning second fastest as he undertook a more normal car evaluation programme for his team.
Under the conditions that teams are operating under this week, those drivers officially classified as youngsters are the only ones who are free to tweak set-ups and evaluate car developments.
The Portuguese driver's best time of 1m33.958s came halfway through the morning, although his total running was limited to just 19 laps.
At Force India, James Calado completed his second morning of running to set the third quickest time of 1m34.013s on medium compounds during that quick spell before lunch.
Pastor Maldonado joined the test for Williams this morning as he too conducted the Pirelli tyre test programme for the team.
The Venezuelan was able to evaluate both compounds, and his best effort of 1m34.116s came on the medium compound in the pre-lunch flurry of activity.
Behind fifth fastest Oliver Turvey, who took over the car after Kevin Magnussen's running on Wednesday, Davide Valsecchi spent time evaluating Lotus's passive DRS system on track.
The concept was used by Kimi Raikkonen in the British Grand Prix, and the team is hoping to make it completely reliable before a likely outing at venues later in the calendar where it will be very useful.
Robin Frijns brought out the only red flag of the morning as he spun the Sauber at Luffield shortly before midday. There was no major damage caused to the car.
Times at 12.30pm
Pos Driver Team Time Laps 1. Daniel Ricciardo Toro Rosso 1m32.972s 48 2. Antonio Felix da Costa Red Bull 1m33.958s 19 3. James Calado Force India 1m34.013s 40 4. Pastor Maldonado Williams 1m34.116s 28 5. Oliver Turvey McLaren 1m34.404s 31 6. Davide Valsecchi Lotus 1m34.440s 38 7. Robin Frijns Sauber 1m34.731s 17 8. Davide Rigon Ferrari 1m34.812s 46 9. Will Stevens Caterham 1m37.301s 33 10. Rodolfo Gonzalez Marussia 1m37.949s 54