Heather Watson the warrior becomes first Briton to win WTA title in 24 years

Gutsy 20-year-old saves four match points to triumph at Japan Open and take place among the world's elite

The greatest year for British tennis in the professional era brought another memorable moment yesterday as Heather Watson ended the country's 24-year wait for a victory on the Women's Tennis Association tour.

Watson's victory in the Japan Open in Osaka was the first by a British woman since Sara Gomer won the Northern Californian Open at Aptos in 1988. The win is likely to take the 20-year-old from Guernsey into the world's top 50 for the first time.

Watson won with a typically battling display in a marathon final against Chang Kai-chen. The 21-year-old from Chinese Taipei is ranked No 134 in the world, but had knocked out Laura Robson and Sam Stosur, the world No 9, and was on the brink of victory in the final when she stood at 40-0 as she served for the match in the deciding set. Watson, nevertheless, hung on and eventually triumphed 7-5, 5-7, 7-6.

The Briton and her partner, 42-year-old Kimiko Date-Krumm, were also in the subsequent doubles final but were beaten 6-1, 6-4 by the Americans Raquel Kops-Jones and Abigail Spears. Watson said afterwards that she planned to go for dinner with Date-Krumm before celebrating with an evening of bowling and karaoke.

Watson has been overshadowed recently by Robson, her 18-year-old compatriot, who beat two Grand Slam champions at the US Open and then became the first British woman to reach a WTA final since Jo Durie in 1990 when she was the runner-up in Guangzhou. Just like London buses, however, you wait an eternity for one and then two come along together as Watson reached the final in Osaka just three weeks later.

The two youngsters have been swapping places at the head of the British rankings this summer and today's updated list will show Watson as the country's top woman again. World No 71 last week, she is expected to climb to No 50 and move above Robson, currently the world No 56.

"When I see somebody doing well I always wants to do better," Watson said. "I was always going to go out there until I had nothing left and they would have had to carry me away on a stretcher. I was going to give it everything.

"British tennis in general is doing so well at the moment, with Andy [Murray] winning the gold at the Olympics and the US Open, Laura doing so well and Johanna Konta qualifying at the US Open and then winning her first-round match. British tennis is doing quite amazingly at the moment. I just hope it continues."

Watson has targeted a place in the world's top 50 all year, but had a minor dip after a memorable Wimbledon, where she became the first British woman to win a match on Centre Court for 27 years and the first to reach the third round for 10. However, she has had a fine run over the last month in Asia. "In the last few weeks I've been saying that it would be really tough to make my rankings target, but now, fingers crossed, I'll be in the top 50," she said.

"At the beginning of this week I felt like I was playing well and my coach even said to me: 'Heather, you're playing well enough to win this tournament. This is your week.' I think everything has gone well this week. I've been stepping up and really playing aggressively. Normally my backhand is my go-to shot, but this week my forehand's been on fire and I've been coming into the net more than usual."

Watson, who will not play again this year, does not have the physical attributes of many of her rivals – she is just 5ft 7in tall and comparatively short on power – but is a superb athlete, a gritty competitor and a player who loves the big occasion. She has always had an appetite for hard work and has been based for the last eight years at Nick Bollettieri's academy in Florida, which is no place for shirkers.

The Japan Open is on the lowest tier of the events on the WTA calendar –Watson's prize money was $37,000 (£23,200), nearly $300,000 less than Murray won as runner-up in Shanghai yesterday – and in truth the field was not strong. Spain's Anabel Medina Garrigues, the world No 40, was the highest-ranked player Watson had to face, with her other four opponents all ranked outside the world's top 70.

The tightness of the final was reflected in the fact that both players won 129 points. Both also dropped serve seven times. Watson had a match point when she served at 5-3 in the second set but double-faulted and lost four games in a row. Chang made the running in the decider and was 40-0 when she served for the match at 5-4. Watson, however, saved four match points and went on to win the tie-break 7-4.

"When I won I almost fell to the ground," Watson said. "I was so happy. I went over to my coaches and I kind of broke down a bit because I was really emotional. I wanted this really badly. I've worked so hard for it."

Heather Watson's rise up the rankings

2009: 588th in the world

2010: 176

2011: 92

2012 (July): 67

Yesterday: 71

Tonight: Top 50