Colin Farrell took part in the Brisbane Marathon Festival

Marathon emcee and running coach Pat Carroll told ABC Radio Brisbane he was calling the race results from the end of the course at Brisbane's Riverstage, and took the opportunity to cheer Farrell home.

He said: "The event was aware that he was running, his team gave them a heads up that he was running. They didn't want it to be made public, probably for a number of reasons - probably one of them being he wasn't even sure he was going to finish."

Farrell completed the 42-kilometre race in just under four hours, finishing 35th out of 64 competitors in the 45-49-year-old race category.

The 'Dumbo' star joined Viggo Mortensen and Joel Edgerton for 'Thirteen Lives', which tells the Than Luang cave rescue in 2018.

The plot centres on the international rescue effort to save a boys soccer team who became trapped in a cave in Thailand after it was flooded by heavy rain.

The rescue made headlines across the globe as all 12 boys and their coach were saved.

Viggo, Colin and Joel will star as rescuers Richard Stanton, John Volanthen and Dr. Richard Harris respectively. Weir Sukollawat, Thiraphat Sajakul, Sahajak Boonthanakit, Vithaya Pansringarm, Teeradon 'James' Supapunpinyo, Nophand Boonyai, Tom Bateman, Paul Gleeson and Lewis Fitz-Gerald will also appear in the movie.

Ron Howard serves as a producer on the project along with Brian Grazer and Karen Lunder for Imagine Entertainment, P.J. van Sandwijk of Storyteller Productions and Gabrielle Tana for the Magnolia Mae banner.