Henao finished fourth with Richie Porte (BMC Racing) taking victory, but the Colombian claimed the yellow jersey as previous incumbent Julian Alaphillippe (Quick-Step Floors) was dropped from the lead group in a dramatic finale.
The Colombian only lost time to Alberto Contador (Trek-Segafredo)and Dan Martin (Quick-Step Floors) on the day, but the time difference ensured Henao moved into the lead from third place.
After a day punctuated by a number of small breaks, the final 16 kilometre ascent was the highest climb in the history of the race and the pressure told as Henao and Mikel Nieve soon found themselves in a leading group after great work from Seb Henao and Phil Deignan to maintain an electric pace.
This selection of riders was then slowly whittled down to an elite group of seven which Porte repeatedly attacked in the closing five kilometres until he was able to get clear of Contador and Henao with just over two kilometres remaining.
While Porte’s GC position ensured the others let him go, Contador was able to steal a mach on Henao to eat into his overall lead, while Martin pipped the Team Sky rider to third to pick up a precious time bonus.
Henao now goes into the final stage with a 30 second advantage over his nearest rival as he aims to record Team Sky’s fifth win in six years at Paris-Nice.