Formula One’s pre-season testing programme finished today with the fourth day of the second test at the Bahrain International Circuit. Mercedes’ Lewis Hamilton set the fastest time of the session though it was a far from faultless day for 2014’s presumptive favourites. Mercedes, however, were not alone in having a troubled end to winter testing, and eight red flags during the day led to the test finishing under floodlights as an extra 25 minutes was tacked on to the end of running time.

The news before the scheduled start was that Sauber had elected to split their day with Adrian Sutil driving in the morning and Esteban Gutiérrez in the afternoon. Sutil did not get a time on the board yesterday as the C33 suffered a failure on its installation lap and was therefore given more time in the car. Also continuing from day three were Sebastian Vettel for Red Bull Racing (scheduled, though he too failed to record a time on Saturday), Nico Hülkenberg for Force India and Romain Grosjean for Lotus.

Elsewhere, the final day of testing saw Fernando Alonso return for Ferrari, Valtteri Bottas for Williams, Jenson Button for McLaren, Max Chilton for Marussia, Kamui Kobayashi for Caterham and Jean-Eric Vergne for Toro Rosso.

After a flurry of early installation laps is was Hülkenberg who completed the first timed lap of the day, setting the standard with 1:38.560. Button and then Bottas went through quicker, with Bottas dropping the benchmark several times to end the first hour of the session with a time of 1:36.281 and thirteen laps on the board. Ten of the 11 teams had appeared at that point, the notable absentee being Mercedes. The team reported it was having gearbox problems and would be delayed in starting its programme.

90 minutes into the session Alonso rose to the top with a lap of 1:35.509. The Ferrari stayed there for 40 minutes before Bottas retook the position with 1:35.153. He subsequently improved on that at noon his best time was 1:34.797.

"We've learnt a lot over the course of these last few weeks and overall it's been a good winter of testing for us."
Lewis Hamilton

The two standout features of the morning were the non-appearance of Mercedes and the unusual situation of the session having run interrupted for three hours from its commencement. Sadly the latter situation was the first to change with Vettel causing the first red flag of the day at 1202. It was difficult to tell what Vettel’s problem had been because while the car appeared to be smoking it also came to a halt pointing in the wrong direction. The team later identified a front-end mechanical issue.

The session was green flagged with a little over 40 minutes remaining before the scheduled lunch break. That was enough time to see Hamilton begin his day in the W05 and also for a second red flag, this time caused by Grosjean halting the E22, causing teams to begin their lunch break five minutes early.

After two red flags in the final hour before lunch, a further six post-lunch made for a disjointed final afternoon, interrupting many teams’ attempts to complete a race simulation. McLaren were responsible for the first with Button parking the MP4-29 after it suffered an engine failure – albeit one attributed to the unit being high-mileage rather than problematic. McLaren mechanics would spend the rest of the afternoon replacing the engine, but Button only had time to add one further lap to his tally, finishing the day with 22 on the board, the lowest of any runner.

The next stoppage was caused by Grosjean, flames visible at the rear of his car. This was proved to be terminal for the E22 and ended the participation of Lotus three hours before the scheduled close. Hülkenberg caused the next red flag with 90 minutes remaining and while fast work by the marshals and Force India crew got the session restarted in quick time, the track went from green to red almost immediately as Alonso stopped the Ferrari.

By this point, however, Kobayashi had passed the 100-lap mark, reinforcing the perception that Caterham, while never troubling the top of the timesheets, was the most reliable of the Renault-powered cars.  Vettel was making up ground after his morning spin, albeit running at reduced speed well off the long-run pace of Red Bull’s rivals.

"We did a lot of laps today so that was useful," said the World Champion when the session concluded. "We tried to do a race distance today; for one reason or another that didn't work out, but in two week's time things should look a little bit different. Obviously it's difficult to know where the car is. It's not just the number of laps you do, but also the type. There are so many different running options, not just with tyres and high or low fuel, there are engine options as well - full power, low power etc, so it's impossible to say where we are. We know we have to catch up in a lot of areas, but that said, I'm happy today, we did a lot of laps, we learned a lot and it was a positive end to a tough week here."

With 25 minutes officially added to the day’s running, Mercedes upped the ante for the final hour and a half by pointing out only 34km separated themselves and Williams at the top of the pre-season mileage chart – but Williams participation in that particular race was hampered when Bottas caused the seventh red flag of the day, stopping on the main straight – this did, however, allow Williams to wheel the car back to the garage without the tow truck, giving them bragging rights of not having troubled the marshals across all 12 days of testing.

"We know we have to catch up in a lot of areas, but that said, I'm happy today, we did a lot of laps, we learned a lot and it was a positive end to a tough week here."
Sebastian Vettel

Running resumed after a very short hiatus but it did so without Caterham, the team calling a halt to their day early with a clutch problem. Force India also stopped early with another component failure put down to high mileage rather than an underlying problem.

With the floodlights coming on Hamilton was making up for his lost morning and set the fastest time of the day with a lap of 1:33.278. This was comfortably quicker than Bottas’ best effort but two-tenths slower than the fastest time of the test set by Felipe Massa on Saturday. There was time before the end for one more red flag – this one intentional as Sauber ran their car out of fuel. The session restarted with 11 minutes remaining and with Red Bull currently bottom of the timesheet. Perhaps considering morale more than engineering necessity, Vettel increased speed in the RB10 for the final minutes and moved up to 9th.

Mercedes ended the 12 days of testing with the most laps completed and the lion share of fastest lap accolades, and so go on to Melbourne perceived to be favorites for victory. Hamilton, however, was downplaying those expectations in his post-session comments:

“This has definitely been the most challenging winter I've experienced and the car is still very much a work in progress,” he said. “We've learnt a lot over the course of these last few weeks and overall it's been a good winter of testing for us. There's been an incredible amount of work put in by the team back at the two factories and on track.

“There's so much to learn with these new cars; it's just mind-blowing and I don't think anybody can be fully ready for the challenge of this season. But I feel as ready as I can be and I'm looking forward to seeing where we are in Melbourne.”

There are 12 days before Friday practice for the Australian Grand Prix.

2014 second Bahrain test day four – unofficial times

1 Lewis Hamilton Mercedes 1:33.278 69
2 Valtteri Bottas Williams 1:33.987 +0.709 108laps
3 Fernando Alonso Ferrari 1:34.280 +1.002 74laps
4 Nico Hulkenberg Force India 1:35.577 +2.299 74laps
5 Jean-Eric Vergne Toro Rosso 1:35.701 +2.423 74laps
6 Adrian Sutil Sauber 1:36.467 +3.189 91laps
7 Max Chilton Marussia 1:36.835 +3.557 61laps
8 Esteban Gutierrez Sauber 1:37.303 +4.025 86laps
9 Sebastian Vettel Red Bull 1:37.468 +4.190 77laps
10 Jenson Button McLaren 1:38.111 +4.833 22laps
11 Kamui Kobayashi Caterham 1:38.391 +5.113 106laps
12 Romain Grosjean Lotus 1:39.302 +6.024 32laps