Cummings top in Portugal

Cummings finished first in four hours, 56 minutes, and 19 seconds, ahead of HTC-Highroad's second-placed Tejay van Garderen and Saxo Bank's Contador in third.

Garmin-Cervelo's Tyler Farrar took the first sprint of the day 10km into the 196km stage - ahead of Omega Pharma-Lotto duo Philippe Gilbert and Andre Greipe - but a group of six riders launched the defining breakaway of the stage two kilometres later.

Martijn Maaskant (Garmin-Cervelo), Anthony Ravard (AG2R La Mondiale), William Clarke (Leopard Trek), Jarl Salomein (Topsport Vlaanderen-Mercator), Jesse Sergent (RadioShack) and Ruben Martinez (Caja Rural) forged a lead of four minutes, before Martinez dropped back after 100km.

Ravard was the next to drop off - after 136km - before the remaining quartet was finally reeled in by the peloton with less than 50km remaining.

At 30km out, Team Radioshack had stretched the peloton into three distinct groups - the front bunch led by Radioshack, Saxo Bank, and Garmin-Cervelo - which remained intact right up to the 2.7km climb up the Alto do Malhao to finish.

Race leader Philippe Gilbert failed to keep pace with a front five of Cummings, Van Garderen, Contador, Cofidis's Rein Taaramae, and HTC-Highroad's Tony Martin - dropping out of contention on the finishing climb - and 29-year-old Cummings timed his final burst to perfection to cross the line first.

"It's a big win for Steve. Today was a hard stage with plenty of tough climbs, especially the final one up to Alto do Malhão," Team Sky's sports Director Sean Yates said after the race.

"When you look at the riders who were around him, to pull out more against them is a fantastic achievement and a very, very impressive performance. He timed his finish to perfection and just jumped them at the end."

Cummings's win also launched him into a six-second lead above Contador at the top of the general classification, with two stages remaining.

1. Stephen Cummings (GBR) Sky Procycling

2. Tejay Van Garderen (USA) HTC-Highroad

3. Alberto Contador (ESP) Saxo Bank Sungard

4. Rein Taaramae (EST) Cofidis, Le Credit En Ligne

5. Tony Martin (DEU) HTC-Highroad

6. Tiago Machado (PRT) Team RadioShack

7. Simon Gerrans (AUS) Sky Procycling

8. Roman Kreuziger (CZE) Pro Team Astana

9. Andreas Klöden (DEU) Team RadioShack

10. Ryder Hesjedal (CAN) Team Garmin-Cervelo