Alexander Albon kept Toro Rosso on top during the final morning of the opening Formula 1 pre-season test of 2019 in Barcelona.
The Anglo-Thai rookie used Pirelli’s C5 tyres – the softest available compound from its reduced range – to post a time of 1:17.637, the fastest of the week so far.
Albon’s pace-setting lap follows on from that achieved by Toro Rosso team-mate Daniil Kvyat on Wednesday, when the Russian headed proceedings.
Daniel Ricciardo finished second for Renault while reigning World Champion Lewis Hamilton was third for Mercedes, as they also joined Albon in the 1:17s.
Charles Leclerc had a brief off through the Turn 5 gravel, and also had a couple of sensors fall from his car, but was able to continue untroubled thereafter and finished fourth, within a tenth of Hamilton.
The Ferrari youngster was the only driver to exceed a race distance worth of mileage during the four-hour session.
Antonio Giovinazzi resumed Alfa Romeo’s programme and finished fifth, with Romain Grosjean sixth for Haas and Red Bull’s Pierre Gasly taking seventh.
Lando Norris caused the only red flag of the session when he went off at Turn 5 just 15 minutes in the session and beached his McLaren in the gravel.
Norris was nonetheless able to resume McLaren’s programme and he placed eighth, ahead of Lance Stroll, who continued Racing Point’s subdued start to the year.
Robert Kubica got his first taste of Williams’ FW42 after the team’s delayed start to testing, and he added almost 50 laps to the car, his best lap 1.5s adrift of ex-Williams racer Stroll.
Testing will resume for another four hours at 14:00 local time.
| Pos | Driver | Team | Time | Gap | Laps |
| 1 |  Alexander Albon |
Toro Rosso | 1:17.637 | 44 | |
| 2 |  Daniel Ricciardo |
Renault | 1:17.785 | 0.148 | 34 |
| 3 |  Lewis Hamilton |
Mercedes | 1:17.977 | 0.340 | 58 |
| 4 |  Charles Leclerc |
Ferrari | 1:18.046 | 0.409 | 75 |
| 5 |  Antonio Giovinazzi |
Alfa Romeo | 1:18.511 | 0.874 | 56 |
| 6 |  Romain Grosjean |
Haas | 1:18.563 | 0.926 | 64 |
| 7 | Pierre Gasly |
Red Bull | 1:19.495 | 1.858 | 52 |
| 8 | Lando Norris |
McLaren | 1:19.543 | 1.906 | 48 |
| 9 |  Lance Stroll |
Racing Point | 1:20.026 | 2.389 | 41 |
| 10 |  Robert Kubica |
Williams | 1:21.542 | 3.905 | 48 |
