As their country prepares to celebrate Bastille Day, Julian Alaphilippe and Thibaut Pinot were in the mood for fireworks a day in advance at the Tour de France.

Key points: Belgian Thomas de Gendt has completed a solo breakaway to claim victory

Belgian Thomas de Gendt has completed a solo breakaway to claim victory Reigning champion Geraint Thomas crashes with 15 kilometres to go

Reigning champion Geraint Thomas crashes with 15 kilometres to go French rider Julian Alaphilippe will wear the yellow jersey on Bastille Day

Carrying the hopes of a country that has not seen a homegrown Tour winner in 34 years, the French pair emerged as the big winners on Saturday of the leg-punishing Stage 8 in Massif Central, which saw Geraint Thomas crash and lose ground in the defence of his title.

After five hours of exhaustion on the saddle across seven short but punishing climbs, Alaphilippe won back the yellow jersey with one of his trademark attacks, while Pinot asserted himself as a strong contender for the final victory, gaining 26 seconds on Thomas and the rest of the group of favourites, including Australian Richie Porte.

"It was a hard day," Porte told SBS shortly after crossing the line.

"It was a full-gas chase behind … [Pinot and Alaphilippe, who] are going well.

"I think going forward, those are the two to watch."

A spectacular rider with an aggressive style, Alaphilippe is, however, limited in mountains and has no real hope of keeping the jersey to the end.

Thibaut Pinot and Julian Alaphilippe became the first Frenchmen in 15 years to sit in 1st and 3rd on general classification. ( AP: Thibault Camus )

Pinot, however, is in the form of his life and can compete with the best above 2,000 metres — an asset giving him hope he can succeed cycling great Bernard Hinault, the last Frenchman to win the Tour in 1985.

Alaphilippe — who won the yellow jersey on Stage three — handed it over after losing just six seconds to Giulio Ciccone on Thursday at the Planche des Belles Filles ski station.

He knew he had a golden chance to get it back on rollercoaster terrain, which suited his skills.

"I will wear the yellow jersey on Bastille Day, for a Frenchman there is nothing better," Alaphilippe said after finishing the stage in third place, just behind Pinot.

Belgian rider Thomas De Gendt, teammate of Caleb Ewan, won the 230-kilometre trek, incredibly holding off the chasing Frenchmen after being a part of a long, four-man breakaway effort at the front.

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With bonus seconds at play at the summit of the final categorized climb, the Cote de la Jaillere, Alaphilippe surged from a small pack of favourites near the top, with Pinot on his wheel.

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The brutal attack was left unanswered after Geraint Thomas' Team Ineos were waylaid by a dramatic crash 15 kilometres from home that saw teammate Gianni Moscon's bike snap in half — and force an intense chase to develop to re-join the pack on the final categorised climb.

"It was a key moment in the race," Thomas said.

"Woods crashed and took out Gianni … and I just got tangled in Gianni's bike."

Alaphilippe went over the mountain in second position behind De Gendt, claiming five precious bonus seconds to turn his deficit to Ciccone into a 23-second lead over the Italian, with Pinot in third place, 53 seconds off the pace.

"By the time I got up to the group I was gassed for a bit and obviously that's when they started to sprint away," Thomas continued.

"It's annoying and frustrating but to come back like I did [is pleasing].

"If I hadn't crashed I could have followed [Pinot and Alaplilippe] and it's a totally different story then."

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Thomas remains fifth overall and 1:12 behind Alaphilippe, conceding just 20 seconds to the Frenchman.

Echoing former teammate Porte, Thomas highlighted the threat that the French pair pose heading into the second week.

"Thibaut Pinot and Julian Alaphillipe have a good kick and punch — they are the guys to watch and beat," he said.

Thomas was involved in another crash during the opening stage last week in Belgium.

This time, he said he was taken out by Michael Woods when the Canadian rider crashed going around a right-hand bend. Woods later rode in with torn shorts.

Determined to shine on a day suited for "bardoudeurs" — a French word used to describe breakaway riders capable of winning on their own — De Gendt spent the day at the front.

The last survivor of a four-man breakaway across the Beaujolais vineyards and the Monts du Lyonnais, he held off the peloton's chase for his second career stage win at the Tour.

Thomas de Gendt celebrates his second career stage victory. ( AP: Christophe Ena )

Australian Michael Matthews led the peloton home in fourth spot, paying credit to his team after they engineered the chase for an elusive stage win.

"We decided to ride to give me a shot at the stage and I think we did a really good job," he said.

"The [general classification] teams took over midway through the day and tried to help and bring the break back … we started pulling straight away to bring back the three guys ahead but unfortunately we fell just short.

"Full respect to the team again for giving it a shot and I'm happy with the legs today."

The stage took a toll on many riders, including former Tour champion Vincenzo Nibali, who conceded 4 minutes, 25 seconds.

A day after his long and unsuccessful breakaway in Burgundy, Frenchman Yoann Offredo struggled with an intestinal bug at the back while pure sprinters including Dylan Groenewegen and Caleb Ewan went through a day of suffering, just making sure they reached the finish within the delays.

Stage results

1. Thomas de Gendt (BEL) — Lotto-Soudal — 5 hours 17 seconds

2. Thibaut Pinot (FRA) — Groupama-FDJ — +6 seconds

3. Julian Alaphilippe (FRA) — Deceuninck-Quick-Step — same time

4. Michael Matthews (AUS) — Team Sunweb — +26 seconds

5. Peter Sagan (SVK) BORA-hansgrohe — same time

General classification

1. Julian Alaphilippe (FRA) — Deceuninck-Quick Step — 34 hours 17 minutes 59 seconds

2. Guilio Ciccone (ITA) — Trek-Segafredo — +23 seconds

3. Thibaut Pinot (FRA) — Groupama-FDJ — +53 seconds

4. George Bennett (NZ) — Jumbo-Visma — +1 minute 10 seconds

5. Geraint Thomas (GBR) — INEOS — +1 minute 12 seconds

18. Richie Porte (AUS) — Trek-Segafredo — +2 minutes 19 seconds

AP/ABC