Serial: 6H  Episode Nos. 602, 603, 604, and 605.  Title: Enlightenment

The White Guardian sends the Doctor to a sailing race with the warning that "winner takes all."  He finds to his astonishment that the apparantly ordinary Earth sailing ships are in fact racing in outer space, and captained by immortal creatures with vast powers but no imagination called Eternals.  They compete for a prize known only as Enlightenment, and the Doctor must stop any of them from winning, particularly the Eternal who is working, as is Turlough,  for the Black Guardian....

starring Peter Davison as the Doctor, Janet Fielding as Tegan, Mark Strickson as Turlough, Valentine Dyall as the Black Guardian, and Cyril Luckham as the White Guardian. Written by Barbara Clegg, Produced by John Nathan-Turner, and Directed by Fiona Cumming.

Originally transmitted from 1 March 1983 to 9 March 1983 on BBC1.