One shot is enough for Tseng to lift British title
The 21-year-old had ended the first day in a share of the lead with Hull and remained at the top of the leaderboard throughout to claim her second major of the year, and her third in total, at Royal Birkdale.
Tseng had started the day with a four-shot lead but bogeys on the third, eighth and 10th holes allowed Hull to reduce the deficit.
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Hide AdAustralian Hull then produced two birdies on the back nine to close the gap to just one shot but the Taiwan player rolled in a six-foot par putt at the last for a final round of 73 and finished on an 11-under-par total to win the title by one shot.
Hull shot a 70 for 10-under with South Koreans Choi Na-yeon (68) and In-Kyung Kim (71) in joint-third place on seven under.
The world No 5, who won 260,000 for her efforts, said: "I was very nervous, especially the last few holes.
"I was so tired, there was so much pressure and expectations – it was an unbelievable day for me.
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Hide Ad"A four-shot lead on this golf course is nothing. She (Hull) really pushed me a lot and it was so close. She was pretty awesome."
Derbyshire's Melissa Reid was the first of the domestic players, a final-round 70 giving her a four-over par total and a share of 31st.
Cleckheaton's Georgina Simpson left disappointed after failing to make the cut by just on shot on Friday night.