Barcelona F1 test day four

00:47 Driver, Team, Time, Tyre
Bottas,Mercedes,1m22.789s,M
Vettel,Ferrari,1m20.241s,S
Verstappen,Red Bull,1m22.058s,S
Perez,Force India,1m21.973s,S
Sirotkin,Williams,1m31.979s,I
Hulkenberg,Renault,1m22.507s,S
Gasly,Toro Rosso,1m22.134s,SS
Magnussen,Haas,1m20.317s,SS
Vandoorne,McLaren,1m19.854s,HS
Ericsson,Sauber,1m23.825s,SS
Hamilton,Mercedes,1m19.333s,M
Leclerc,Sauber,1m22.808s,S
Stroll,Williams,1m21.142s,S
Sainz,Renault,1m20.940s,M
Alonso, McLaren,1m20.929s,SS

20:16 Here's our report from the day - did Mercedes fire a warning shot with that pace on mediums? We'll find out a lot more next week when we get more running and the first proper race simulations, which offer proper clues about pace on various fuel loads. Autosport and Motorsport.com will bring you full live coverage again next week, and until then keep checking back to get all the latest from this week's opening action of 2018:

F1 testing: Hamilton tops final day of first test on medium tyres

Lewis Hamilton topped the final day of the opening 2018 Formula 1 pre-season test at Barcelona for Mercedes

20:09 That was a seriously busy day for the teams, with 15 drivers being put to work. We suspect that's a taster for what we have in store next week when the hope is all four days will take place in decent weather. There'll be lots happening.

20:01

20:00 And there's the chequered flag. Hamilton ends the last day of the first pre-season test the way he ended last season - top of the pile.

19:58 We stand corrected! Hamilton is back out. Two minutes to go...

19:57

19:55 Hamilton pits for what we assume will be the last time. He's completed 68 laps, just over a grand prix distance.

19:54 Vettel nudging back into the 1m20s, but nowhere close to his personal best. Track temps are down to 13.3C so any improvements in the last five minutes would be a surprise.

19:52 Hamilton has taken over from Vettel as the fastest on track for now, both are in the 1m21s.

19:51 We're into the final 10 minutes and the track is just about as busy at it's been all day. Hamilton, Vettel, Magnussen, Alonso, Sainz, Gasly and Leclerc are all out pounding in the laps.

19:47

19:46 Vettel just came within a tenth of his personal best, he's the quickest on track at the moment by some margin - although Hamilton is now out again with 15 minutes left to run.

19:42 The track's pretty busy as we enter the final 20 minutes of running, with Vettel, Alonso, Sainz, Stroll and Gasly all out. But nobody is looking much like improving.

19:39

19:38 Lap count:

Gasly 128
Vandoorne 110
Vettel 100
Magnussen 83
Ericsson 79
Hamilton 61
Bottas 60
Perez 60
Hulkenberg 49
Sirotkin 47
Stroll 44
Leclerc 42
Sainz 42
Verstappen 35
Alonso 33

19:37 Alonso is going for a run on softs - a relatively hard choice of compound by McLaren's standards this week - and he's doing low 1m22s.

19:34 Magnussen, Stroll and Gasly get out there too.

19:31 McLaren are the first to get back out there with Alonso. Vettel is next up.

19:30 The teams didn't seem to appreciate that briefest of red flag periods. Nobody has taken up the offer to head straight back out as we enter the final 30 minutes.

19:28 Bizarre. Leclerc was the last car back, but he wasn't sporting any signs of having had an off.

19:28 And now we have a green flag.

19:28 We're not entirely sure what this red flag is for - all the cars are back in the pits.

19:26 Red flag.

19:25 Hamilton's times continue to improve on this run - 1m20.4s last time around.

19:24 Not for the first time today, Leclerc is lapping pretty slowly on ultrasofts. Hopefully for Sauber's sake those are planned high-fuel runs. The F2 champion has been one of the most aggressive when it comes to weaving on the start/finish straight to generate some tyre temperature.

19:23

We haven't seen a flash of pink in a while, so here's Perez negotiating the chicane at the end of the lap (LAT Images)

19:20 Hamilton is gradually winding things up on this run, he's now in the high 1m20s.

19:16 Low 1m22s for Hamilton at the start of this latest medium-tyre run.

19:14 Another small improvement for Stroll. He's still... you guessed it: seventh.

19:14

Vettel is now up to third for Ferrari with three quarters of an hour remaining (LAT Images)

19:13 More medium-shod running for Hamilton and Mercedes. Today's pacesetter is back on track.

19:11 Stroll wants to get in on the act of improving laptime but not position. With a 1m21.2s he stays seventh.

19:10 Another small improvement for Vettel. He stays third, 0.9s behind Hamilton. Vandoorne still sits between them owing to his hypersofts effort earlier.

19:06 Vettel jumps Magnussen next time around with a 1m20.2s.

19:05 Magnussen and Vettel improve, but they stay third and fourth, now separated by 0.074s.

19:05

19:03 Race control hasn't had too many difficult decisions to make this week, but have you ever considered what it might be like for those in charge over the course of a race weekend? Thanks to F1 Racing, here's a look at how a grand prix is run: