How triathlon works at the Olympics:

The men's and women's races will feature 55 starters apiece.

The venue is London's Hyde Park.

The race starts with a 1.5km open water swim, followed by a seven-lap 43km road cycle and a four-lap 10km run. The bike and run courses are basically flat.

"T1", the swim-bike transition, and the bike-run "T2" are critical parts of the race where valuable time is won and lost.

There are strict rules governing transition, such as when triathletes can put on and take off their helmets, and the time penalties involved can be decisive. A potential nightmare scenario for the sport is if a time penalty affects the top results.

Drafting on the bike, or pack riding, is often illegal in the sport - but it is a fundamental part of Olympic triathlon.