Defending champion Katie Boulter edged out Harriet Dart in a marathon all-British tie to reach the second round of the Nottingham Open.

Opening her grass-court season, third seed Boulter won 6-7 (5-7) 6-4 7-5 in a contest lasting three hours and 13 minutes.

British number one Boulter’s victory in Nottingham 12 months ago marked her first WTA title.

The 27-year-old will play Viktorija Golubic of Switzerland or Canada’s Rebecca Marino next.

“That was an absolute battle,” said Boulter, ranked 30th in the world.

“[Dart] is an incredible grass-court player. I tried to do the best I could because she was playing seriously good stuff.

“I would have taken a much easier win, that’s for sure. I’m not sure I’ve seen a three hour, 13 minute grass-court match. I’m not sure that’s possible.”

Both players struggled to hold serve in the opening set, with four breaks apiece before a tie-break was needed to separate them.

Searching for a quick response, Boulter broke Dart’s serve in the first game of the second set before holding to end a run of five consecutive breaks.

During a lengthy seventh game in which she twice saved break point, Dart repeatedly argued with the chair umpire over what she believed was an incorrect, “embarrassing” line call.

Their heated discussion continued into the change of ends, with Dart offering a £50,000 bet that the ball in question was out.

An unperturbed Boulter proceeded to serve out the set at the first opportunity to force the decider.

She broke early on and looked to be taking control, only for Dart bring the set back on serve in a drawn-out sixth game, doing so on her fifth break point.

But Boulter soon broke again and served out the win on her third match point.

Earlier, British number five Heather Watson progressed to the second round with a 4-6 6-0 6-4 rain-disrupted win over American Kayla Day.

Watson will next face sixth seed Karolina Pliskova of the Czech Republic.

Fellow Briton Emma Raducanu will begin her Nottingham campaign on Tuesday against Japan’s Ena Shibahara, while top seed and world number 10 Ons Jabeur opens against Colombia’s Camila Osorio.

Elsewhere, Jack Draper got his grass season off to a winning start, reaching the second round of the Stuttgart Open where he could meet fellow Briton Andy Murray.

British number two Draper defeated Austrian Sebastian Ofner 7-6 (7-4) 7-6 (7-5).

“When it came down to it, I’m glad I competed really hard and got over the line. It’s good to be back on the grass,” Draper, 22, said in his on-court interview.

Murray starts his Stuttgart campaign against American Marcos Giron on Tuesday.

The 37-year-old is preparing for what looks set to be his final Wimbledon, having previously said he does not plan on “playing much beyond the summer”.

He will team up with brother Jamie in the men’s doubles at Wimbledon in what will be their first Grand Slam appearance as a pair.

Earlier this month, Jamie Murray told BBC Sport it was “now or never” for the brothers to play together.

Wimbledon starts on 1 July.