Storer, riding for Team DSM, was part of a 29-rider breakaway which emerged following the first of six climbs on the 152-kilometre route from Gandia to Balcón de Alicante.

Four other Team DSM riders were in the group, but race leader Primož Roglič of Jumbo-Visma and Slovenia was not.

Valverde, fourth in the general classification entering the stage, was also back in the peloton but attacked on the second climb.

It proved a costly decision, as the 41-year-old Spaniard crashed on a bend was ultimately unable to continue, abandoning the race.

Hugh Carthy of Britain and EF Education Nippo - third in the general classification in 2020 - also bowed out today.

Back in the breakaway, Storer, the Russian Ineos Grenadiers cyclist Pavel Sivakov and American EF Education Nippo rider Lawson Craddock broke away again, before Storer and Sivakov dropped Craddock on the final climb.

Lotto Soudal's Dane Andreas Kron and Carlos Verona from Movistar and Spain caught the front two, but Storer kicked once more 3.5km from the line and nobody was able to match the Australian's pace.

Storer won in 4 hours 10min 13sec, 21sec clear of second-placed Verona and 59sec ahead of Sivakov.

The general classification finished 3min 33sec behind the stage winner, with Roglič retaining the red jersey but now just 8sec clear of Felix Großschartner, the Austrian in Bora-Hansgrohe colours.

Movistar Spaniard Enric Mas is third, 25sec behind Roglič.

Egan Bernal, the Colombian Ineos Grenadiers rider who has won the two other Grand Tours, is 41sec back in sixth.

Today's stage win is Storer's first at a Grand Tour.

Tomorrow's stage, a 173.7km ride from Santa Pola to La Manga del Mar Menor, looks to favour the sprinters.