Geraint Thomas’s final test to winning the 2018 Tour de France could be stage 19 over the Tourmalet and Aubisque, but at least he can rely on four-time victor Chris Froome to guide him through.

Thomas leads the Tour de France after 18 days with 1-59 minutes over Tom Dumoulin (Sunweb) and 2-31 over his Sky team-mate Froome in third place.

The last mountain day remains on Friday before a time trial stage and the flat finish in Paris on Sunday.

“Hopefully we won’t have to use Froomey and we will have strength in numbers and he’ll be able to follow as well, but having Froomey as my disposal is phenomenal,” Thomas said.

“It’ll be a big test. It’s one for the team to control for most of the day. The last climb will mostly down to the legs. It’ll be good to just keep doing what we’ve been doing.”

Froome already rode in support of his Welsh team-mate trying to win his first Grand Tour. In stage 17, Froome followed rival Primož Roglič (LottoNL-Jumbo) when he attacked on the final Col du Portet climb.

Looking slightly below his best, Froome faded at three kilometres from the top.

He should lend a hand to Thomas if needed on Friday. He will also try to maintain his third spot or re-take the second place that he lost on the Col du Portet to Dumoulin.

Stage 19 covers the big passes Aspin, Tourmalet, Bordères, and the Col du Soulor leading to the Aubisque at 1,709 meters. It descends the last 20 kilometres to Laruns.

“I think we are expecting the worst, and hoping for the best. We are expecting a lot of attacks from the guys, especially on the Tourmalet, and certainly on the last climb,” Thomas said.

Geraint Thomas leads Chris Froome and Primoz Roglic on Alpe d’Huez at the 2018 Tour de France (Sunada)

“It’s the last mountain stage, and guys are going to try to take as many opportunities as they can, but in the back of their minds, they are still going to have the TT [31km on Saturday]. They can do a big move to tomorrow and then still lose a chunk of time in the TT.

“We’ve been riding well in the race so far, so let’s hope we can keep it together again tomorrow.”