Great Britain are in control of their Billie Jean King Cup play-off against Mexico after victories for Katie Boulter and Heather Watson on the opening day in London.

At a near-deserted National Tennis Centre, Boulter marked her return to the competition with a 7-5 6-0 victory over Marcela Zacarias before Watson saw off Giuliana Olmos 7-5 6-1.

One more victory in Saturday's reverse singles, or the deciding doubles should the tie go that far, would see Britain earn another shot at qualifying for the elite finals week in 2022.

Captain Anne Keothavong acknowledged on Thursday that, following the switching of the tie from Mexico to Britain, her side were heavy favourites.

Both teams were missing their leading player, with Johanna Konta choosing to practise outdoors on clay at the same venue to give her troublesome knee time to adapt to the surface, while Renata Zarazua also cited knee issues in her decision to skip the tie.

Boulter is only the British number nine but was given the nod over Harriet Dart, Jodie Burrage and Katie Swan to make her first appearance in the competition – formerly known as Fed Cup – since aggravating a back injury in the 2019 victory over Kazakhstan.

She has struggled to get her ranking up since returning to the sport at the end of that year and remains at 291, six places below Zacarias.

But Boulter's resume indicated she should come out on top and so it proved, although she was twice a break down in a tight opening set and had to save multiple break points at 5-5.

That proved to be the crucial moment, with Boulter breaking serve to win the set and then overpowering Zacarias in the second as she showed the sort of form that carried her into the top 100 two years ago.

The 24-year-old said: "I was a little bit nervous at the start. Obviously the occasion, I knew what it was and I wanted to play my best tennis. Sometimes it's difficult to do that and I knew she was going to be a tough opponent.

"Of course it was natural to have nerves and I felt like a dealt with them really well and managed to tough out the first. That gave me a lot of momentum and gave me the confidence to go into the second, and I thought I played some really good tennis in the second set.

"I've been doing that day in, day out on the practice court, it's just a matter of doing more and more of it on the match court."

The players' team-mates and support staff were the only ones able to provide vocal backing, but that was certainly appreciated by Boulter.

"Honestly it felt great out there," she said. "We've been playing with basically no one pretty much every week. Sometimes it can feel a little eerie. It felt really nice having the team behind you and some noise and some atmosphere."

Watson's 22nd singles victory in the competition moved her clear of captain Keothavong into second place in the all-time British standings behind Virginia Wade.

It followed a similar pattern, with Watson edging a tight first set against a player ranked more than 350 places lower before pulling away in the second.