The MTN-Qhubeka rider fought back after he was dropped by Thibaut Pinot (FDJ) and Romain Bardet (AG2R) to claim a historic Tour de France win for the African team on a day they remembered former South African President Nelson Mandela.
The general classification battle generated a standings shakeup when Nairo Quintana (Movistar) moved up to second place overall after an attack directed at race leader Chris Froome (Sky) in the final few kilometres of the sstage which put several of the key contenders under pressure.
Froome responded and matched the diminutive Colombian climber with each pedal stroke, but Alberto Contador (Tinkoff-Saxo), Tejay van Garderen (BMC) and Vincenzo Nibali (Astana) had trouble responding to the intensity of the assault.
Froome leads Quintana by 3min 10sec with van Garderen dropping to third at 3min 32sec. Alejandro Valverde also put in a strong performance and is now fourth at 4min 2sec.
The 178.5km stage from Rodez to Mende started inauspiciously with a crash after just 5km which knocked FDJ’s Steve Morabito out of the race with a broken collarbone.
An initial small break of five riders became a larger one of 20 riders, including Cummings, Pinot, Bardet, Peter Sagan (Tinkoff-Saxo) Rigoberto Uran (Etixx-QuickStep), Greg van Avermaet (BMC), Koen de Kort (Giant-Alpecin), Simon Yates (Orica-GreenEDGE) and Bob Jungels (Trek Factory Racing).
Later it split again as Uran, Andriy Grivko (Astana), Matthieu Ladagnous (FDJ), Ruben Plaza (Lampre-Merida) attacked with an immediate response coming from Sagan, Jungels and Jarlinson Pantano (IAM) to hook back on as the intermediate sprint approached. Behind, the remaining group of riders languished between them and the peloton.
Sagan’s stage intent was clear when he extended his green jersey lead with an uncontested win ahead of Plaza and Grivko at the intermediate sprint which came after 78km of racing.
By the time the race reached the Category 2 Côte de Sauveterre it was clear the winner would come out of the break, with Sagan and van Avermaet again hot favourites to repeat their Stage 13 battle despite the severity of the 10 per cent finishing climb.
The detente of the break cracked with 15km to go when Michal Golas (Etixx-QuickStep) then Kristjian Koren (Cannondale-Garmin) attacked on the Côte de Chabrits well before the final ascent on the Côte de la Croix Neuve.
The response came with less than 4km left to race with attacks from Bardet and Pinot which stretched the break into ones and twos on the road.
Several riders tried to bridge to the French pair but only Cummings had the resolve to take them on along their preferred terrain.
Dateline special: Tuesday 21 July 9:30pm on SBS