Our reporters Saiqa Chaudhari, Craig Nelson and Jeremy Culley will be blogging live from Ironman from 6am today.
More than 2,000 athletes complete a 2.4 mile swim, 112 mile cycle and 26.2 mile run from 6am
Competitors have 17 hours to complete the challenge, and expect to burn 20,000 calories.
The first athlete is expected to finish at about 2.30pm in Victoria Square
Platt Lane in Westhoughton, from North Road to Park Road, will close from 6am to 9am to allow cyclists to pass through safely
Chorley New Road will be closed all day for the marathon, from the A58 junction at Beaumont Road to the junction with St George’s Road and Chorley Old Road.
Passengers who usually get on or off buses on Chorley New Road can catch a replacement shuttle bus service between 11am and 11.30pm.
Marshals will be present to allow access for emergency services, residents, and businesses.
Middlebrook Retail Park is open as usual.