The 31-year-old Ryf, world Ironman champion in 2015, 2016 and 2017, produced an extraordinary performance to clock 8 hours 38min 44sec at the finish line in the heart of the old city in what was her first ironman of the season.

Ryf, who was seventh and 40th respectively in the Beijiing 2008 and London 2012 triathlons, finished almost half-an-hour clear of her nearest challenger, Sarah True, who clocked 9:05:19.

Australia’s 35-year-old Sarah Crowley took third place in 9:12:31.

Frodeno, 36, won the Beijing 2008 triathlon title and has since won the world Ironman title twice, in 2015 and 2016, as well as setting the world record of 7:35:39 in 2016.

Patrik Nilsson of Switzerland was second in 8:08:15, with Frodeno's big rival and fellow German Patrick Lange, the current world Ironman champion, third in 8:09:26. 

Male and female athletes began with a 3.8 kilometres swim course in the quiet waters of the Langener Waldsee.

The two-loop course had a short run between the laps.

The two-loop, 180km bike course took the field through the middle of Frankfurt, and into surrounding small villages.

The course, which was closed to traffic, was hilly and challenging, mixed with some flat sections.

Thousands of spectators came out to cheer for the athletes.

The 42km flat run course consisted of four fast laps, which allowed athletes to reach their best marathon times.

The running course was also lined with thousands of spectators enjoying the sunshine as they gathered along the promenande next to the river.