Britain's Steve Cummings won his first stage at the Tour de France as leader Chris Froome extended his lead.
MTN-Qhuebeka rider Cummings, 34, was part of a 20-man breakaway and overhauled Romain Bardet and Thibaut Pinot with a late surge to the line.
Froome extended his lead in the yellow jersey to three minutes 10 seconds as Tejay Van Garderen struggled on the steep climb to the finish in Mende.
Movistar's Nairo Quintana finished behind Froome and is now second.
The dramatic stage win and late drama among the yellow contenders ensured a gripping last hour of a stage that was watched by France's President Hollande.
Yellow jersey battle intensifies
Froome has been at the top of the general classification since German Tony Martin crashed out of the race at the end of stage six.
He has been well protected by team-mates throughout the race so far but found himself isolated at the bottom of the steep 3km climb up the Cote de la Croix Neuve at the end of the 178.5km stage from Rodez to Mende.
Quintana immediately launched an attack, with defending champion Vincenzo Nibali following him. They put some distance into Froome but the 30-year-old maintained a steady rhythm and gradually hauled them back.
By the time the yellow jersey contenders approached the finish, Froome and Quintana had pulled away. Froome sat on Quintana's wheel before sprinting past him to finish one second ahead of his rival.
But it was far from a bad day for Quintana, who moved into second after BMC's Van Garderen struggled to keep pace with the late surge.
"It was another hard day but we stuck together well and got Froomey into position at the bottom of the climb and it was up to him then," said Team Sky's Geraint Thomas.
"He ended with more time on second place, which is great."
After the finish Froome revealed that he had a cup of urine thrown at him by a spectator earlier in the stage.
A perfect finish for Cummings
There was aggressive riding with a flurry of attacks from the very start of Saturday's hilly stage.
An early crash led to the withdrawal of Swiss rider Steve Morabito with a broken collarbone - but the stage eventually settled down into a group of 20 riders that built a sizeable lead over a peloton controlled by Team Sky and seemingly content to let them pull away.
The group included green jersey holder Peter Sagan - who was first across the day's intermediate sprint to extend his lead over Andre Greipel in the points classification - as well as Colombian Rigoberto Uran Uran and French duo Bardet and Pinot.
As the group closed on the finish it became increasingly evident that they would not be caught.
Pole Michal Golas and then Slovenia's Kristijan Koren burst off the front of the breakaway and the two of them were together with 13km left and led at the bottom of the climb up to Mende.
They were eventually caught by Bardet and Pinot and it looked as though the French riders would contest the stage but they hesitated as they jockeyed for position. That proved costly as Cummings, a former world team pursuit champion, accelerated past them and held on for the most famous win of his career.
Who is Steve Cummings?
Cummings becomes the 12th British rider to win a stage at the Tour de France after the most notable victory of his road racing career.
The 34-year-old Merseysider was a member of Team Sky in their inaugural 2010 season and was with the team when he finished ahead of Alberto Contador to claim a mountain-top finish in the 2011 Tour of Algarve. In the same year he finished second in the Tour of Britain.
Cummings has also raced for Landbouwkrediet-Colnago, Discovery Channel, Barloworld, BMC and is now with South Africa-based MTN-Qhuebeka.
On the track, he won the team pursuit at the 2005 World Championships in Los Angeles and at the 2006 Commonwealth Games, where he also took bronze in the individual pursuit.
"The last few years I have thought I'm capable of doing this [a stage win], I just needed to find the right team to give me the opportunity," said Cummings after his victory on Saturday.
"Before the top I thought I had got a bit of a chance - the co-operation between Pinot and Bardet was bad and enabled me to catch them. I threw caution to the wind and went straight away."
Mandela Day magic
African team MTN-Qhuebeka might have been a wildcard entry into this year's Tour but they are enjoying a race around France to remember.
First Eritrean rider Daniel Teklehaimano took the polka dot jersey at the end of stage six - in the process becoming the first black African to top the King of the Mountains standings.
|Bicycles for the underprivileged|
|Qhubeka is a word from the language of the Nguni people of southern Africa that means "to carry on", "to progress", "to move forward". Qhubeka is a foundation that provides bicycles as a means of transport to underprivileged populations.|
And they could not have picked a better time to claim their first Tour stage win as Saturday's stage took place on Nelson Mandela Day.
"I gave a talk this morning on Mandela Day and the significance of Mandela Day and what he's done in the world and to South Africa, and our team was so pumped," said boss Doug Ryder.
"The dream goal was just to be here. To win a stage, we were just thinking: 'Wow, this would be nice.' Unbelievable. What a day! It means so much. It just shows that African cycling needs to be in the world."
Thrown out for hitching a ride
It was not such a good day for Bretagne Seche Environment's Eduardo Sepulveda.
He broke a chain 57km from the finish and took a ride of approximately 100 metres in an AG2R La Mondiale team car from his broken bike to his waiting team car.
Tour rules do not allow any rider to be driven during a route and so the Argentine has been thrown off the Tour.
Bretagne Seche manager Emmanuel Hubert said: "Instead of walking towards me he climbed in the AG2r car. They did 100 metres so that's the rules, he's out of the race."
Stage 14 result
1. Steve Cummings (GB) MTN-Quebeka 4hrs 23mins 43secs
2. Thibaut Pinot (Fra) FDJ +2secs
3. Romain Bardet (Fra) AG2R +3secs
4. Rigoberto Uran (Col) Etixx - Quick-Step +20secs
5. Peter Sagan (Slo) Tinkoff-Saxo +29secs
6. Cyril Gautier (Fra) Europcar +32secs
7. Ruben Plaza (Spa) Lampre
8. Bob Jungels (Lux) Trek
9. Jonathan Castroviejo (Spa) Movistar
10. Simon Yates (GB) Orica-GreenEdge +33secs
General classification after stage 14
1. Chris Froome (GB) Team Sky 56hrs 02mins 19secs
2. Nairo Quintana (Col) Movistar +3mins 10secs
3. Tejay van Garderen (US) BMC Racing +3mins 32secs
4. Alejandro Valverde (Spa) Movistar +4mins 02secs
5. Alberto Contador (Spa) Tinkoff -Saxo +4mins 23secs
6. Geraint Thomas (GB) Team Sky +4mins 54secs
7. Robert Gesink (Ned) LottoNL +6mins 23secs
8. Vincenzo Nibali (Ita) Astana +8mins 17secs
9. Tony Gallopin (Fra) Lotto +8mins 23secs
10. Bauke Mollema (Ned) Trek +8mins 53secs