Aru was not coming back, however, celebrating victory on the same climb former team-mate Vincenzo Nibali had won on, also in the Italian champion’s jersey, back in 2014.
Martin kicked to claim second place, while Froome snaffled the final bonus points ahead of Porte.
Six seconds later, Yates led Uran and Contador across the finish line to move into the white jersey, while Thomas was tenth – 40 seconds behind Aru on the stage.
Froome, as a result, will now wear the yellow jersey and will expect to keep it for at least the next three days with the next mountain test not coming until stage eight on Saturday.
The last two riders to pull on the yellow jersey after La Planche des Belles Filles, however – Sir Bradley Wiggins and Vincenzo Nibali – have held it all the way to Paris.
And Froome is keen to retain the jersey as long as possible. He said: “I’m obviously really happy to be back in yellow. I’m going to try and defend the jersey as long as I can. It’s not a new feeling being in yellow, it’s something we’ve worked very hard for and I’m going to try and keep it as long as possible.”
Tour de France 2017: stage five – result
1) Fabio Aru (ITA) – Astana – 3.44.06hrs
2) Dan Martin (IRL) – QuickStep Floors +16″
3) Chris Froome (GBR) – Team Sky +20″
4) Richie Porte (AUS) – BMC Racing – ST
5) Romain Bardet (FRA) – Ag2r-La Mondiale +24″
6) Simon Yates (GBR) – Orica-Scott +26″
7) Rigoberto Uran (COL) – Cannondale-Drapac – ST
8) Alberto Contador (ESP) – Trek-Segafredo
9) Nairo Quintana (COL) – Movistar +34″
10) Geraint Thomas (GBR) – Team Sky +40″
1) Chris Froome (GBR) – Team Sky – 18.38.59hrs
2) Geraint Thomas (GBR) – Team Sky +12″
3) Fabio Aru (ITA) – Astana +14″
4) Daniel Martin (IRL) – QuickStep Floors +25″
5) Richie Porte (AUS) – BMC Racing +39″
6) Simon Yates (GBR) – Orica-Scott +43″
7) Romain Bardet (FRA) – Ag2r-La Mondiale +47″
8) Alberto Contador (ESP) – Trek-Segafredo +52″
9) Nairo Quintana (COL) – Movistar +54″
10) Rafal Majka (POL) – Bora-hansgrohe +1.01