Britons Heather Watson and Aljaz Bedene reached the second round at Wimbledon, but compatriot Laura Robson is out after an erratic display.
British number two Watson, 25, beat Belgium's Maryna Zanevska, the world number 119, 6-1 7-6 (7-5).
Bedene overcame Croatian 21st seed Ivo Karlovic in an epic five-set encounter that lasted for over four hours.
Earlier, Robson paid for a string of unforced errors as she lost 6-4 6-2 to Brazil's Beatriz Haddad Maia.
Four of the seven British players in action on day one progressed, with defending champion Andy Murray and Johanna Konta joining Watson and Bedene in round two.
- Murray opens Wimbledon defence with win
- Konta races through first round
- Relive the action from day one at Wimbledon
Robson determined to revive career
Since reaching the last 16 here in 2013, 23-year-old Robson has struggled for form and fitness and her world ranking has dropped to 189.
She matched Haddad Maia for power, but made far too many unforced errors.
Robson received noisy support from home fans on Court 18 but lost to the world number 97 in one hour and six minutes.
"I didn't feel like I played at the level I can and it wasn't the way I've been playing in the last few weeks," said the 2008 girls' champion.
"I feel I let myself down a bit and didn't get into the match. I tried to play too perfect when I didn't need to go for so much.
"She didn't have to do a lot, I gave her all the chances she wanted."
Robson insists she has the appetite to resurrect her career.
"I enjoy tournaments and enjoy grinding through as many matches as I can," said Robson, who reached a career-high ranking of 27 in July 2013.
"I hope I can get my ranking up so I don't need a wildcard and feel like I deserve to be here."
Former British number one Sam Smith
"Laura Robson looks very fragile and there is a long way to go before we see her in the top 100.
"Twenty-three unforced errors is the story of the match - she just made too many errors.
"If you are a Robson fan, do not give up hope. There are still a few glimmers there that the tennis is good, but the confidence is so low.
Watson gets over the line... eventually
Watson has slipped out of the world's top 100 but reached the semi-finals at Eastbourne last month and maintained that form here.
Until her recent return to form, Watson had also endured a difficult few months after winning the mixed doubles title at SW19 in 2016.
She has struggled to see out matches from commanding positions and it was the same story here, after a run that saw her take 16 out of 17 points on her serve in the second set.
Watson served for the match at 5-1 5-4, but squandered three match points and her confidence wobbled before she recovered to wrap up the match in the tie-break.
The world number 102 left the court grinning broadly and will play either Yulia Putintseva of Kazakhstan or Latvia's Anastasija Sevastova, the 18th seed, in round two.
"Apart from the odd wobble here and there, that was an outstanding serving performance by Heather Watson and that could send her a long way in these Championships," said Smith.
"Off the back of her great week on grass in Surbiton and, in particular, Eastbourne, I am very pleased to see her building on that.
"This always looked like a winnable first-round match for Heather, but she had to go out there and do it - and she had to play pretty well to reach the second round."
Bedene battle went on and on
Bedene came through an epic battle with Karlovic, winning a war of attrition with the 6ft 11in Croat that lasted four hours and 24 minutes.
Both players were dominant on serve, with 38-year-old Karlovic firing down 44 aces to Bedene's 27, and neither man managing a break until the very end of the match.
Bedene, who is Slovenia-born but took UK citizenship in 2015, finally made a breakthrough with two blistering return winners at deuce at 7-6 in the fifth set.
The world number 58 won 6-7 (7-5) 7-6 (8-6) 6-7 (9-7) 7-6 (9-7) 8-6 and will play Damir Dzumhur of Bosnia and Herzegovina in round two.
Three-time Wimbledon champion John McEnroe told BBC Sport: "Bedene is deservedly thrilled to win but so are all the other top-ranked players because you don't want any part of this - this guy's serve is probably one of the top three or four greatest serves in the history of tennis, even at the age of 83 or whatever he is."
Brits Broady and Norrie go out
British wildcard Cameron Norrie was beaten in the first round, losing 6-3 6-2 6-2 to Frenchman Jo-Wilfried Tsonga.
Norrie, a 21-year-old student in the United States who only turned professional last month, was beaten in one hour and 22 minutes by the two-time Wimbledon semi-finalist.
It was a tough first test at a Grand Slam for Norrie, who was born in South Africa, raised in New Zealand and now lives in America but, with a Scottish father and Welsh mother, represents Britain.
"I played one loose service game in each set and it cost me," said Norrie. "I'm not used to playing guys at this level.
"I think I matched him pretty well. The whole match was just his serve, and he stayed focused and on it the whole match. He didn't give me anything. But it's a good learning experience."
Naomi Broady failed to reach the second round for the fifth time in six visits to Wimbledon, the 27-year-old from Stockport beaten 6-4 6-2 by Romanian Irina-Camelia Begu.
Broady was let down by her serve and also made a number of disappointing errors.