British number one Johanna Konta earned her first win at the Battle of the Brits team event with an impressive comeback against Katie Boulter.
Konta, playing in only her second match since March, trailed by a set and double break before fighting back to win 2-6 7-6 (7-5) 10-6.
The 29-year-old's win helped extend her British Bulldogs team's lead to 14-4 against the Union Jacks in Roehampton.
Bulldogs' Cam Norrie, Liam Broady and Maia Lumsden also won singles matches.
The unique event features the country's leading men and women at the National Tennis Centre, split into two teams chasing points in singles, doubles and mixed doubles matches.
The event has been organised by Jamie Murray to provide competitive action for British players while the professional tours remain suspended because of the coronavirus pandemic.
"It's not what it would feel like at a Grand Slam or WTA event but it was good to give us both of us the chance to get those competitive juices and pretend we're somewhere else," said Konta after beating 23-year-old Boulter.
"She started very well but I felt I improved as the match went on and by the end we were playing some great tennis.
"These are my first competitive matches since the beginning of March so it is going to take time. I was in a good mindset and I stayed in each point and gave myself the best chance for my level to get better."
British men's number one Dan Evans, representing the Union Jacks, takes on former world number 14 Kyle Edmund later on Tuesday.
Three-time Grand Slam champion Andy Murray is playing in the mixed doubles alongside youngster Jodie Burrage at about 19:00 BST.
Murray, 33, is playing only in the doubles because he does not want to take any risks with his fitness.
Tuesday's order of play
Union Jacks 4-14 British Bulldogs
(Results/matches show Union Jacks players first, with points available in brackets)
Centre court (play starts at 11:30 BST):
Jan Choinski 4-6 3-6 Cameron Norrie (two)
Katie Boulter 6-2 6-7 (5-7) 6-10 Johanna Konta (one)
Naomi Broady/Heather Watson v Harriet Dart/Beth Grey (two)
Not before 16:30 BST: Dan Evans v Kyle Edmund (three)
Andy Murray/Jodie Burrage v Joe Salisbury/Emma Raducanu (two)
Court one (play starts at 11:30 BST):
Anton Matusevich 1-6 6-2 10-12 Liam Broady (one)
Alicia Barnett 7-5 4-6 7-10 Maia Lumsden (one)
Jamie Murray/Olivia Nicholls v Alastair Gray/Eden Silva (one)