TARA MOORE caused the biggest upset of the AEGON GB Pro-Series Barnstaple tennis tournament so far.
The British No 6, ranked 244 in the world, beat fourth seed Jana Cepelova, the world No 107 from Slovakia, 6-2, 2-6, 6-3 at the Tarka Tennis Centre.
Moore, 20, was a break down twice in the deciding set but reeled off four games in a row to lead 5-2 before serving out the win.
She was the second Briton through to the next round after Naomi Broady beat Lina Stanciute, of Lithuania, 6-3, 6-3.
Broady, who has been struggling for form this year, impressed against the 2008 semi-finalist, serving well and overcoming a wobble in the second set when Stanciute came back from 4-0 down to 4-3.
On the first day of the main-draw action there were also wins for Madison Brengle, Ekaterina Bychkova, Vesna Dolonc and Eleni Daniilidou who beat last year's runner-up Marta Domachowska.
In the second round, Moore will meet the winner of today's match between Jill Craybas and Marta Sirotkina. Broady will face Russian opposition in the shape of either Nina Bratchikova, the No 2 seed, or qualifier Mayya Katsitadze.
Anne Keothavong, the British No 3 and reigning champion, starts her defence of the Dartington Vase against Latvia's Diana Marcinkevica today, third on Court Two after the 11am start.
AEGON GB Pro-Series Barnstaple - 1st round: Madison Brengle (USA) beat Elitsa KOSTOVA (Bul) 6-1, 6-3; Ekaterina Bychkova (Rus) beat Tereza Mrdeza (Cro) 6-1, 7-5; (6) Eleni Daniilidou (Gre) beat Marta Domachowska (Pol) 6-4, 6-2; Tara Moore (GB) beat (4) Jana Cepelova (Svk) 6-3, 2-6, 6-3; (8) Vesna Dolonc (Srb) beat Akgul Amanmuradova (Uzb) 6-3, 6-2; Naomi Broady (GB) beat Lina Stanciute (Ltu) 6-3, 6-3.