10:45 Welcome back to AUTOSPORT Live as we continue to follow the opening day of practice for the 2010 Gulf Air Bahrain Grand Prix.

The Formula One teams have been very busy over the past two-and-a-half hours, but are ready to receive the next challenge - that of improving their performance in this afternoon's session.

The extended Sakhir circuit has thrown up some small surprises already today and more are sure to follow as the teams and drivers continue working on the general set-up of the car, as well as completing tyre comparison tests and running with varying amounts of fuel on-board.

Conclusions are difficult to draw from the first session, with the potential for huge differences in fuel loads, but more answers may be forthcoming over the next 90 minutes.

10:46 Adrian Sutil was the front-runner at the end of a busy first practice session earlier today, as the teams got their first taster of the extended Bahrain International Circuit.

Pre-season testing indicated that Ferrari and McLaren would be right at the top, and initially this proved to be the case once the obligatory rush of installation laps was completed.

The Lotus pairing of Heikki Kovalainen and Jarno Trulli acted as unwilling track sweepers for the field, but it wasn't long before Lewis Hamilton moved to the top of the order. He was quickly usurped by new team-mate Jenson Button as the McLaren inter-team rivalry began to take shape.

But then came the Ferrari response. Fernando Alonso ousted both British drivers by the midway point, with team-mate Felipe Massa also enjoying a fruitful run on his competitive return to the sport.

With Mercedes duo Schumacher and Rosberg having been out and placing themselves close to the top two teams, the Force India drivers then appeared. They made an instant impression ...

Tonio Liuzzi swiftly moved into the top ten, but Adrian Sutil stole the show with some consistently quick laps - his quickest being 1m56.583s. Alonso was second, just under two-tenths of a second shy of the German, with Robert Kubica a creditable third on his Renault debut.

10:48 Weather conditions remain very warm and sunny, with temperatures climbing to 30 degrees Celsius - a complete contrast to what the teams faced at the pre-season tests.

Several centimetres of snow fell at Barcelona's Circuit de Catalunya earlier this week, but conditions in Sakhir couldn't be better for the opening round of the season.

Following practice, we will have a detailed look at the forecast for the rest of the weekend in our Bahrain Grand Prix Weather page.

10:50 AUTOSPORT forum members are invited to join the fun throughout the weekend, offering thoughts and opinions as the event unfolds.

• Who will come out on top at the end of this afternoon's session? Can we really expect Force India to stay at the front? Are fuel loads masking the true order? Will the bigger teams move to the fore?

• Red Bull and Mercedes would appear to be chasing the front-runners so far. Is this a sign of early trouble as far as this weekend is concerned, or do you expect them to be fighting for victory as the weekend goes on?

• The new teams all ran this morning without any obvious signs of trouble - a good early start for all of them. Our new team question today is about HRT F1. Will Bruno Senna and Karun Chandhok manage to post some lap times on the board?

Tell everyone what you think.

Click the SHOW LIVE FORUM link in the red bar at the bottom of your browser window if you would like to join the debate.

10:51 Some highlights from the first practice session of the season:

• Michael Schumacher was tenth on his return to the sport, completing 16 laps of the track with a best time of 1m57.662s. However, the German was reportedly far from happy at the end of his first run. He later went out and improved slightly, but will be looking for much more significant improvements this afternoon to stay with the leaders.

• The newly-announced Hispania Racing Team created a slice of history this morning. The Senna name returned to Formula One as Ayrton's nephew Bruno completed a successful shakedown of the car in full public gaze. The late deal to bring the team to the sport resulted in no pre-season testing, but the team did a great job and Senna completed three trouble-free laps without setting a time.

• Lotus driver Heikki Kovalainen completed the most laps of anyone this morning. The Finn totaled 21 tours of the circuit, closely followed by German newcomer Nico Hulkenberg with 20. The top nine drivers on the time sheet were covered by just 0.672 seconds - more evidence that we are in for a close and exciting season. May it continue!

• Throughout the pre-season tests, Lotus and Virgin were locked in a battle to be the best new team, with Lotus usually coming out on top. But in first practice it was a reversal of fortune, as Timo Glock gave first blood to Virgin, with a lap almost two-tenths of a second quicker than Heikki Kovalainen.

10:53 With a reduced allocation of 11 sets of slick tyres per driver this year, and one set of the prime tyres already discarded after first practice, drivers now have a set of both the harder and softer rubber to evaluate this afternoon.

As tyre degradation under a heavy fuel load is now key to determining the strategy for the race, there is a lot of milage to complete in this second session.

Crucially, the teams also need to know how the car will work with heavy fuel on the softer tyres, so don't expect to see much in the way of low fuel laps this afternoon. If some do try lighter runs, it is likely to be on tyres already used on a heavy fuel test.

The teams need to learn so much about how the two compounds react with various fuel loads that they are likely to split programmes between the two drivers more than ever before.

10:53 Some insight from Mike Gascoyne at Lotus: "Second session starting in 15 mins, all ready to go. Long runs to check Tyre degradation and brake wear. Still difficult to work out where everyone is due to different fuel loads"

10:55 There are just five minutes to go before the action resumes at the Bahrain International Circuit.

10:56 The ambient is up to a sizzling 33 Celsius, warming the asphalt to 46 degrees.

10:59 Jenson Button steps back into his McLaren to get ready for his afternoon of work.

0 min: The practice session is underway.

0 min: Meantime, HRT F1 driver Karun Chandhok is standing in his civvies, watching over the progress of the team, as they continue to prepare his car.

0 min: Jaime Alguersuari gets proceedings underway. He practices a start and joins the racetrack.

1 min: The Spaniard is alone on the circuit at the moment, but we expect more drivers imminently.

2 min: Vitaly Petrov heads out in his Renault for the first time this afternoon.

2 min: Mark Webber is rolling down the pitlane. He joins the early runners.

3 min: Tonio Liuzzi comes out in the Force India. It will be interesting to see how his first run this afternoon goes.

4 min: Jaime Alguersuari starts his first flying lap, and is immediately confronted by a nightmare, as he comes across all those drivers who have just joined the circuit.

4 min: Lucas di Grassi joins the circuit in his Virgin machine, making it nine cars on track already.

4 min: Alguersuari just manages to negotiate his way through the slower traffic, as he continues on this first timed lap.

5 min: Alguersuari completes that first lap and the time is 2m02.757s.

5 min: Mark Webber and Sebastian Vettel are immediately back into the pits after a single installation lap.

5 min: Petrov has a problem with his Renault - the headrest foam has come loose on the main straight and he will be pitting to have that fixed.

6 min: Liuzzi is instantly quick in the Force India. He is set to top the times in the early stages.

7 min: Indeed, Liuzzi tops the list with a 1m58.53s lap.

7 min: Jaime Alguersuari has improved on his second timed lap with 2m01.775s. He is now second to Liuzzi.

8 min: Di Grassi gets his name on the timesheet with a 2m03.955s effort.

8 min: Alonso and Massa, along with Hamilton and Button are all on track now.

9 min: Adrian Sutil joins the pack in the other Force India. Nico Hulkenberg is also out there.

9 min: Liuzzi does not manage to improve on his second timed effort but remains top of the list.

9 min: Button is the fastest man through all three sectors on his first timed lap of the session, topping the order in 1m56.944s.

9 min: Alonso has slotted in third quickest, with team-mate Massa fourth in the early order.

11 min: Lewis Hamilton is now quickest through the first sector as he begins a flying lap.

11 min: Nico Hulkenberg goes quickest of all with a lap of 1m56.799s for Williams. Team-mate Barrichello is also on the circuit.

12 min: Hamilton is also on top through the second and third sectors to take away the best time. A 1m56.051s is the new benchmark from the McLaren.

13 min: Button is quicker than his team-mate though the first sector of his latest lap. Over the line, he slots in second quickest, almost half a second down.

14 min: Barrichello is up to fourth quickest in his Williams.

15 min: Replays show the Lotus of Trulli shedding a piece of bodywork along the front straight.

16 min: Hamilton heads to the pits in his McLaren, telling his team that the "rears are destroyed". He has completed four laps on the harder option.

17 min: There is a clear band of graining on Hamilton's right rear as his McLaren is pushed into the garage.

17 min: Meanwhile, Nico Rosberg has topped the order in his Mercedes with a lap of 1m55.555s.

19 min: Michael Schumacher springs up to third quickest with a 1m56.504s lap.

19 min: HRT's Jose Ramon Carabante has explained the situation in his team to reporters:

"Bruno is going out again and we hope that in half an hour Chandhok will be able to go out too. There's a small problem that they are trying to solve and there's still hope that he will go out."

21 min: Down in the Virgin garage, Timo Glock's car is being worked on and the German has not been out so far in this session.

22 min: Recent efforts from Vettel in the Red Bull have put him up to sixth quickest with a best of 1m56.924s, but he has just run wide in the final corner.

24 min: Massa is now 10 laps into his afternoon, testing the long run pace of the F10.

25 min: Lucas di Grassi is trying the super soft rubber on his Virgin.

27 min: Hamilton is back on track and clocks the fastest first sector.

28 min: Replays show Hamilton running wide as he tests the super soft rubber for the first time, spoiling that lap in the lengthy middle sector.

28 min: Button is also testing the softer tyres on the McLaren.

29 min: Massa continues his long run on the harder tyre.

31 min: Hamilton reports that the rear end of his car is bottoming through Turn 6, where there is a major bump in the early part of the new section of track.

32 min: This will be a big concern for the teams as they have to get the ride-height of the cars correct to cope with the full-race fuel load.

33 min: Bruno Senna is now out in the HRT, clocking a slow time of 2m10.352s.

33 min: With just over half an hour gone, Rosberg heads the order from Hamilton, Button, Schumacher, Hulkenberg and Vettel.

35 min: Track conditions will continue to improve as the drivers pound around on long runs this afternoon.

35 min: Fernando Alonso is back on track to try the super soft tyres on his Ferrari.

37 min: Team-mate Massa continues a lengthy run on the harder compound and has completed the most laps - 16 - this afternoon.

37 min: Rosberg is now on the softer rubber and quicker still - 1m55.409s is now the benchmark time.

38 min: Senna pits after his first run in the HRT and has improved to a 2m09.115s but is still over 13 seconds off the pace.

39 min: Michael Schumacher is another man testing the super softs and he improves in third quickest with a 1m55.903s.

41 min: Nico Hulkenberg has used his latest run to move up to fifth quickest with a best of 1m56.799s.

41 min: Massa has pitted after his long run, while team-mate Alonso is lapping on the softer tyres.

43 min: Jarno Trulli studies the data down in the Lotus garage. He is currently 20th on the timesheet, with team-mate Kovalainen 19th.

46 min: Timo Glock is getting ready for an outing in the Virgin Racing car.

47 min: Petrov is up to fifth quickest with 1m56.750s effort in the Renault.

49 min: The McLaren pair of Hamilton and Button are back out for some more running.

50 min: Jaime Alguersuari has a narrow miss with the barriers in his Toro Rosso as he just misses the barrier after a major spin.

52 min: Robert Kubica is out running in the Renault and improves to a 1m59.826s for 13th quickest.

53 min: Mark Webber is chatting to the team on the Red Bull pit wall and it looks like his car is being worked on in the garage.

54 min: Pedro De la Rosa clocks a 1m59.495s in his Sauber to go 12th quickest.

55 min: Felipe Massa is now trying the softer tyres on his Ferrari but has been for a minor off-road excursion in the final corner.

57 min: Karun Chandhok isn't having a great debut so far and it looks like the HRT driver won't make it out today as the team struggle to get his car ready for action.

57 min: The track is pretty busy now as teams cram in as much running as possible to get an idea of how the tyres perform this weekend.

58 min: Vettel is out with super soft rubber on the Red Bull. He has been struggling with brake issues so far this morning, while team-mate Webber is currently sidelined with technical issues.

60 min: Vettel is another man to run a little wide though the final corner, but continues.

62 min: Senna is back out in his HRT and is closing in on the 2m08.459s that was the quickest time set by Oliver Turvey in GP2 Asia practice this morning.

63 min: Long runs continue, with the McLaren and Mercedes duos all simulating race stints.

67 min: Little change to the headline times as the business of heavy fuel testing plays out.

68 min: Rosberg remains on top with a 1m55.409s from Hamilton, Schumacher, Button, Vettel, Hulkenberg and Petrov.

69 min: De la Rosa improves in the Sauber while testing the super softs. He's now eighth on a 1m57.287s, just ahead of team-mate Kobayashi.

69 min: Senna has finally beaten this morning's GP2 pace, clocking a 2m07.876s.

71 min: The McLaren pair continue their long runs while both Mercedes are back in the pits.

73 min: Buemi is also yet to set a time this afternoon and his Toro Rosso is undergoing major repairs in the garage.

75 min: Alonso is out for a run on the harder tyres, while most drivers put laps on the softer rubber.

76 min: All the teams will have a great deal of data to evaluate after this session to plan their tyre use for the rest of the weekend.

78 min: Alonso is currently tucked up behind Vettel's Red Bull, who has just been in a traffic tussle with Rosberg's Mercedes.

81 min: Alonso is now clear of the Red Bull and sets his fastest time through the first sector.

82 min: Alonso improved to 11th quickest with a 1m57.415s

82 min: All but Lewis Hamilton from the top 15 are on track for a busy close to the session.

85 min: Drivers continue to put a final series of laps in the books as they test the long run pace on heavy fuel loads.

87 min: Hamilton has ended his running earlier than most of the others and is chatting to the engineers in the McLaren garage.

87 min: Nico Hulkenberg is testing the softer tyres and reports to the team that the "rears are going away a lot"

89 min: The session has ended. Cars that have already started a lap may complete it.

89 min: Into the final minute of the session and Massa has set his fastest first sector on super soft tyres.

12:31 Massa remains seventh as a session of long runs comes to an end.

12:31 Nico Rosberg tops the timesheet this afternoon from Hamilton, Schumacher, Button and Vettel.

12:32 Bruno Senna has shot off into the run-off at Turn 1 after something appears to have broken on the right rear of the HRT.

12:33 The Brazilian has stepped out of the car and there is clearly work to be done to investigate that problem.

12:34 The teams now have a great deal of data to pour over after extensive running this afternoon.

12:37 The afternoon round-up is now available:

Rosberg quickest in second practice

12:38 @redbullf1spy explains some of the lost running today: "Mark's was a precautionary stop for his gearbox and Seb had to change his brakes."

12:39 So a busy first day of practice in Bahrain draws to a close but it is difficult to judge the pecking order after so much running on various heavy fuel loads.

Qualifying will reveal much more, but before that is the final practice session. Join us for coverage from 07:45 GMT tomorrow.