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Aston Martin's hopes of winning the LM GTE Pro category appear to be over after the sole #97 took to the pit lane with technical problems whilst in the midst of a thoroughly entertaining battle with the #51 AF Corse Ferrari.
Starting the hour with Bruno Senna in the lead, the Brazilian was caught and passed by the fast-approaching Gimmi Bruni, only for him to remain latched onto the back of the Ferrari and snatch back the initiative 20mins later.
With both drivers setting fastest laps of the race, it seemed to be a battle that was destined to rage to the finish before Senna pitted with smoke seeping from the engine bay.
Despite no evident loss of pace, the car was wheeled into the garage, where remained for almost 25mins having dropped to fourth in class. It has since re-joined but is continuing to suffer issues.
At the top of the leaderboard, things remain static with the #1 Audi – still being driven by Gene - leading the way by a lap over the #20 Porsche, now driven by Timo Bernhard.
The lead of LMP2 could also be about to change after the #35 OAK Ligier was wheeled into its garage. The car, which has run without fault all race, has a one lap lead over the sister TDS Ligier, which in turn gained a spot during the hour at the expense of the Signatech Alpine after it developed issues and slipped to fourth in class.
Bruni now leads GTE Pro by a clear two laps, though Aston Martin still commands a similar advantage in the GTE Am class.
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full updates after each hour
Live text commentary recap of Hour 19: Key moments in bold
Seems the #97 Aston Martin's problems could be more terminal... smoke is reported to be coming from the rear again
Philippe Thriet brings his eponymous car into the pits for a stop. He just needs to get back out and complete one more lap to claim the LMP2, unless OAK Racing can get the #35 car going again
Meanwhile, the #97 Aston Martin is back on track after nearly 25mins in the pit lane. Darren Turner is now in the car, but is five laps down in fourth
Drama in LMP2, the leading #35 OAK Ligier is wheeled into the garage and the engine cover is off...
The #2 Audi is in the pit lane - Fassler hands over to Lotterer
The #97 Aston Martin is still in the pits and has slipped to 4th in class, behind the #92 Porsche and the #73 Corvette
Dumas pits the #14 Porsche from fifth place and hands over to Neel Jani
The LMP2 leading OAK Ligier pits and returns to the track with Jann Mardenorough still at the wheel - it remains a lap up on the sister TDS car
Big shame for Aston Martin and for us too! It was the only close lead battle no track and it had entertained from the very start
His misfortune means Bruni moves into a clear GTE Pro lead, particularly as the next best car - the #92 Porsche - is two laps behind
The car was smoking when it came in, which has prompted Aston Martin to play caution and take a look under the bonnet - rotten luck for Senna, who has been driving a blinder today
Senna in the Aston Martin has pitted from the lead of GTE Pro... and it is in the garage!
Webber pits the #20 Porsche and hands over to Timo Bernhard
Bruni elects to dip out of that lead battle and heads for the pit lane
The Signatech Alpine has rejoined the race and is running fourth in the LMP2 class, but is a lap down on the top three now having been up in second place
Senna sets his fastest lap of his race - and the fastest lap of the GT class in this race - en route to passing Bruni for that lead
Senna and Aston Martin are back ahead in the GT class, passing Bruni's Ferrari down the straight. Game on!
The race leading #1 Audi pits for its 24th stop of the race
Usually it is the other way around, but the GTE battle was briefly spoiled by the LMP1 cars as Fassler and Lapierre squeezed themselves in between the feuding Ferrari and Aston
Bruni sets his fastest lap of the race... despite having the Aston Martin of Senna crawling all over the back of his Ferrari!
The Signatech Alpine remains in the pit lane, which has allowed the JOTA Zytek up into third position in the LMP2 class
Webber has picked up the pace and is lapping on a par with the #1 Audi, but there is no indication that it can mount challenge on speed alone. Fassler, meanwhile, is still the quickest driver on circuit
Less than six hours to go... or, the same length as a regular WEC race!
We are well into the final quarter of what has turned out to be a very exciting and unpredictable 2014 Le Mans 24 Hours to go
Bruno Senna is not giving up on the GTE Pro lead - he is still latched onto the back of the Ferrari that just passed him
The Signatech Alpine has made its way back to the pit lane under its own power... just not a lot of it. Into the garage it goes
The #2 Audi pits from third place - Fassler will stay in the car
It has already ceded a place to the #46 TDS Ligier and is down to third
The Signatech Alpine, which was running 2nd in the LMP2 class, is reported to be slow on track
Bruni takes the lead of the GTE Pro class for the #51 AF Corse Ferrari team, Senna unable to match it under braking