Geraint Thomas held off the challenge of Alberto Contador to win the Paris-Nice by only four seconds on Sunday.
The Team Sky rider started the seventh and final stage with a 15-second advantage over the Contador, but the Spaniard looked to set to win the famous race for a third time when he attacked on the last two climbs.
Tinkoff rider Contador put Thomas under real pressure in a dramatic finale, but the two-time Olympic track gold medallist from Wales was not to be denied what he labelled as the biggest victory of his career.
Richie Porte and Tim Wellens also dropped Thomas on the final two climbs, only for the 29-year-old to muster one last effort with the help of a depleted Team Sky squad to reduce the deficit and claim the yellow jersey.
Thomas worked with team-mate Sergio Henao and Tony Gallopin (Lotto Soudal) to claw back time on the final descent of the 141 kilometre stage and ensure Contador and Porte had to settle for second and third place respectively.
Tim Wellens (Lotto Soudal) claimed the stage victory, but it was very much Thomas' day as he ensured a Team Sky rider has now won the Paris-Nice in four of the last five years.
Thomas said: "When Alberto went, we took it calmly at first but then on Col d'Eze, I must admit my legs gave way and I really thought it was over even for the podium.
"But then in the descent, I must really thank Sergio, this yellow jersey also belongs to him. This is amazing. It's definitely the greatest win in my career so far.
"To win ahead of Alberto, who is one of the greatest stage racers ever, and Richie, who won almost every race he entered last year, I can hardly believe it. I came there obviously wanting to do my best but to actually do it... I'm over the moon."