Baltacha is ranked over 200 places behind Keothavong

Baltacha, ranked 412 after struggling with injuries and illness, saw off world number 179 Keothavong 6-2 2-6 7-6 (7-5) in round one.

The Scot recovered from a break down in the decider after Keothavong needed an injury time-out when 5-4 in front.

Katie O'Brien beat Vasilisa Bardina 7-5 6-3 to re-take the British no. 1 spot.

Baltacha goes on to face fifth seed Nicole Vaidisova in the last 16.

The win is a huge boost for the 23-year-old, who had a major back operation last year after previously suffering with a liver condition.

"I'm very proud but I made it hard for myself after such a great start," said Baltacha. "Anne started very slowly and I got straight in there but after the first set I started to try to get a bit safe and go on the defensive.

I've improved my confidence a lot here Katie O'Brien

"But it is a wonderful result even though I played a very sloppy tie-break as well until right at the end.

"There were a lot of points on it and the 130 world ranking places I will go up means it is now about 270 from 890 which is where I was six months ago after my back operation.

"I feel I'm a better player now than when I was 170 or so, a few years ago, but I know I've got to keep working on it.

"Whatever happens in the next round against Vaidisova, who is talented and very dangerous, I'll be staying here for the rest of the week because the courts are just like Wimbledon and it is fantastic preparation."

Keothavong said: "I'm not going to feel down just because I lost this match. There were only a few points in it and if I'd been just a little more aggressive I'd have won.

"I strained a quad in a fall and it definitely had an effect on the result."

O'Brien, 21, now meets former US Open and French Open finalist Elena Dementieva in the second round.

She said: "I'll give it my best shot. I've improved my confidence a lot here and learned a lot about myself.

"I don't have a coach and have been travelling the world on my own. You go to places like China and Chinese Taipei trying to pick up rankings points and it is the loneliness that gets you.

"So it is great when you can come to places like Eastbourne and Wimbledon and do well. I think I've deserved it.."

O'Brien's win means there are three British players in the second round at Eastbourne for the first time since 1991.