Change in yellow...Tour blown wide open!

A change in the race lead shouldn't come as a major surprise. I mean, Fabio Aru did only trail Chris Froome by 18 seconds coming into the stage. And yet, I'm still shocked that it has happened, and I don't quite know why? Aru has looked excellent thus far in this race, winning a stage, while Froome has failed to isolate the Italian when given the chance. With the stage win going to Romain Bardet ahead of Rigoberto Uran with Aru two seconds behind in third and Froome 7th at 22 seconds, Aru is into yellow. He leads Froome now by 6 seconds. Bardet is still in third, but only 25 seconds behind, with Uran a further 30 seconds back.

The big losers on the day were Nairo Quintana, Alberto Contador and Jakob Fuglsang. Quintana lost 2'04" and is now 8th at 4'01" on GC, Contador lost 2'15" and is 11th at 7'14", while the injured Fuglsang lost 27'42".

The change in race lead means Sky have lost the jersey for the first time this race. Had they gone from start to finish in the lead it would have been the first time since the Faeme team did it in 1970. Tomorrow will be the first time in 26 stages dating back to last years Tour that a Sky rider hasn't held the jersey. Beyond that, it is the first time Froome has lost the race lead to another rider since stage 4 of the 2015 Tour when Tony Martin took the race lead. He had never lost it to a GC rival before today.

Do you get the sense that the tide is shifting?

Anyone who dismissed this Tour as over when Froome donned the yellow jersey last week, will now find themselves crawling back to see what is going to happen. With four men within a minute of the race lead this is setting itself up as one of the closest Tour battles in years. Froome has a fight on his hands if he wants a fourth title. With a time-trial to come on stage 20, Froome might yet be good for at least another minute, but there is a lot of climbing between now and then.

Tomorrow's stage is a mere 101km in length but includes three category one climbs before a downhill finish. The pace will be frantic from the start as riders look to isolate one another. It was a stage I felt that Froome's rivals might try to isolate him. As it turns out it might be the stage Sky need to isolate the rest.

Froome still looks a gear below is best. The argument will be whether he can find that gear or not. Was today his bad day, or is it a sign? There has been a suggestion that Froome is riding himself into top form this year, highlighted by the fact he was below the boil in the tune-up races. The thought is that he will peak for the third week and explode on the likes of stages 17 and 18. On the other hand Froome might already have hit his peak and may need to find other ways to out smart his opponents. We already seen shades of that last year. And it will be a big ask to do, as Aru is looking strong and there is no reason to suggest he will fade as the race goes on. Stages 16 and 17 will suit him too, with stage 17 in particular looking good for Bardet. That descent alone could see him net 30 seconds if he plays it right.

Everything will be won and lost and it looks now as though the time-trial will play a factor. Whether it will see Froome having to regain time remains to be see in the days ahead. The first half of this Tour may have belonged to the sprinters as people yawned their way through repetitive flat stages, but the narrative is turning towards the GC men now.

This Tour is wide open.

General classification after stage 12:

1. Fabio Aru (Astana) in 52h51'49"

2. Chris Froome (Sky) +6"

3. Romain Bardet (AG2R) +25"

4. Rigoberto Uran (Cannondale) +55"

5. Dan Martin (Quickstep) +1'41"

6. Simon Yates (Orica) +2'13"