By Chris Bevan
BBC Sport at Wimbledon
Keothavong will play four-time champion Venus Williams in round two
British number one Anne Keothavong had to dig deep to see off Vania King and reach the second round at Wimbledon for only the second time in eight attempts.
King edged an error-prone first set but the big-hitting Londoner fired off 18 winners as she won the second set.
King battled on in the decider but Keothavong came through 4-6 6-2 6-3 and will play Venus Williams in round two.
Meanwhile Katie O'Brien threw away a 5-0 second set lead to lose 6-3 7-5 to 24th seed Shahar Peer.
As the number 92 in the world, Keothavong had become the first British woman since Sam Smith in 1999 to qualify for the main draw at the All England Club automatically.
With her opponent ranked just one place below her, there was little between the two players but Keothavong's attacking approach from the baseline eventually paid dividends.
King, who had only won one match here herself in two previous visits, got to the net whenever possible but began making more mistakes as Keothavong raised her game.
The 24-year-old from Hackney had to keep her focus in a tight third set but, with King struggling to hold her serve, she capitalised to wrap up a hard-fought victory.
"I'm just pleased to get through," Keothavong said.
Can I beat Venus? There is not much point me going out on court if I don't think I am going to win
"It was incredibly tight in the first set and it was a horrible feeling to lose it but I managed to regroup and turn the match around.
"I took some time out after the first set and I was in the toilet shaking because I was so annoyed with my performance at that point.
"I had played so badly because of a combination of nerves and the expectations I had of myself. I put quite a lot of pressure on myself but in the end I came through."
Keothavong faces an even stiffer challenge next in the shape of four-time champion Williams, who kicked off the defence of her title by beating British number five Naomi Cavaday.
"I am excited about playing Venus next," Keothavong added. "Big matches like that are the reason I play tennis and I have got nothing to lose.
"I am sure I will speak to Naomi about how she got on - I heard she put up a good fight.
"Can I beat Venus? Yes. There is not much point me going out on court if I don't think I am going to win."
O'Brien failed to match last year's performance of reaching the second round when she suffered a dreadful second set collapse against Peer.
After taking a 2-0 lead in the first set she dropped her serve at the wrong time to lose the first set.
She then took total command of the second set by rattling off the first five games but she failed to finish it off and Peer staged an incredible comeback to wrap up the match.