The American timed her race to perfection to snatch the women’s PTWC crown from reigning world champion Lauren Parker on the line.

Parker was more than three minutes ahead of Gretsch after the swim only to see that lead come under increasing pressure as her rival clawed her way back.

It was a thrilling finale as Gretsch narrowly beat Parker to the finish line, claiming victory by the narrowest of margins.

Gretsch came home in 1hour 6min 25sec - one second ahead of Parker who had to settle for silver.

The 29-year-old’s victory comes after she won two gold medals at the Pyeongchang 2018 Winter Paralympics.

She is only the fifth American to secure titles in the Winter and Summer editions of the Paralympics.

Eva Maria Moral Pedrero of Spain was more than eight minutes behind Gretsch and Parker, finishing in 1:14.59 to clinch bronze.

Jetze Plat of The Netherlands triumphed in the men’s PTWC2 final, beating Austria’s Florian Brungraber by two minutes.

The Dutch triathlete claimed victory in 57:51 with Brungraber coming second in 59:55 and Italy’s Giovanni Achenza picking up bronze in 1:02:05.

Germany’s Martin Schulz has defended his men’s PTS5 title after seeing off the challenge of Britain’s George Peasgood.

Schulz crossed the line in 58:10 to claim gold as Peasgood had to settle for silver in 58:55.

The bronze medal went to Canada’s Stefan Daniel who clocked 59:22.

After Peasgood’s silver, Britain completed the set of medals in the triathlon, securing gold and bronze in the women’s PTS5.

Lauren Steadman claimed silver at Rio 2016 after making a costly mistake when she made a wrong turn in the water.

She was not to be denied the title this time around and crossed in a winning time of 1:04.46.

Grace Norman of the US finished second in 1:05.27 with Claire Cashmore ensure another British medal with bronze in 1:07:36.