With 60 laps to go, the cars started a round of green flag stops, briefly giving Marco Andretti (who had been up to third and running strongly) the lead as the stops cycled through. And it was another poor stop for an element of the Penske line-up - who had come into this race as the favourites - when Helio Castroneves stalled and had to be refired. A very costly error.
At least Ryan Briscoe got through unscathed again, and indeed was one of the last to pit showing how well he was conserving fuel while still able to run up with the leaders. Unfortunately that luck came to a crunching end the minute he returned to the track, hitting the wall on the front straightaway on lap 147 and annihilating the right side of his car on the safety barrier. It looked as though the accident was possibly the result of pushing the tyres too far before they got up to temperature.
Briscoe had left a lot of debris and oil on the track, meaning a lengthy yellow flag period while the track was cleaned up. It was still too far from the chequered flag to make it by refuelling at this point, so most of the field stayed out and Dario was still in the top spot and rapidly pulled away from the field when the track went green on lap 156; Marco Andretti had returned from his previous stop in second place, but Tony Kanaan quickly wrested the position back from him.
The green flag was shortlived, as Sebastian Saavedra ended up spinning and planting the back of the 78 into the wall on lap 160. This time, the front runners all pitted and there was considerable congestion in the pit lane that saw Ryan Hunter-Reay and Scott Dixon make contact. Will Power also had to return to pit lane next time round to replace a wheel - not a good day for the Aussie.
Several backmarkers stayed out, including Brits Mike Conway and Justin Wilson who led the field back to green and also giving Dario Franchitti the unfamiliar scenario of being stuck in among traffic in fifth. Would that put him of his stroke and leave him vulnerable to a charge by Tony Kanaan?
Conway was obviously far short on fuel and came in to the pits with 22 to go, the gambit of hoping for another caution not paying off. Wilson and Rahal made it to 10 to go, handing Helio Castroneves the lead briefly until the Brazilian's own pit stop two laps later. But fuel was marginal even for those drivers who had pitted under the last caution, and frantic calls were being broadcast from pit wall to all the drivers to get them to lift and conserve. Just when they most needed one, yellow flag caution periods were hard to come by.
Kanaan couldn't make it - he was in on lap 195, five short of race distance. And even Franchitti was on a knife edge, the Ganassi team finally ordering him to slow dramatically as they entered the final couple of laps. Further back, Dan Wheldon - not in danger on fuel - saw the opportunity to put the pedal to the metal and go for it, cutting chunks out of Franchitti's lead. If Dario really has nothing left in the tank, then he was a sitting duck. All that could save him now was a yellow flag.
Which is exactly what he got. As the leaders started the final lap, a massive accident was sparked by Mike Conway going into the side of Ryan Hunter-Reay. The angle was such that Conway was lifted up and launched into the air, spinning around wildly until he was collected by the wire fencing which duly tore the car apart, and then dumped the wreckage down on Hunter-Reay. A very, very nasty accident (which also collected others such as Helio Castroneves with debris and panicked avoidance measures, as well as a couple of fans from airborne debris that escaped the catch-fence). Conway's chassis was left upside down and the safety crews scrambled to extricate him, and for a moment the outcome of the race was secondary - but fortunately Conway was out and waving to the crowds moments later, clearly awake and alert albeit with a confirmed broken right leg and hence airlifted to hospital shortly after.
With relief that everyone was safe, the celebrations for the Flying Scotsman for his second Indy 500 victory (the first was in 2007) could begin, joined by his jubilant team boss Chip Ganassi and ecstatic wife, actress Ashley Judd. And in a day that had seen two Brits come top in the F1 Turkish GP half a world away, it seemed that the feat had topped by the Indianapolis 500 which saw not only Franchitti first and Dan Wheldon second, but their compatriot Alex Lloyd initially posted as coming third. However, a post-race hearing found that Marco Andretti had actually been running in third when the crash happened and that he had been wrongly overtaken during the confusion that ensued, so Marco had the position handed back by the race stewards with Lloyd fourth ahead of Scott Dixon (Ganassi) and Danica Patrick (Andretti).