Alan Yentob concludes the series with a look at the crusading heroes who seek truth, protect the innocent and do the right thing - the cops, the cowboys, the doctors and the spooks.

The line separating the hero from the villain has often been a fine one in American history, and the ambiguities that lie at the heart of heroism have inspired some of primetime's most popular and long-running shows, including MASH, The X Files, 24, NYPD Blue and The Wire.

From the white-hat versus black-hat pieties of the 1950s to the gritty dilemmas of the post 9/11 world, this episode talks to the stars, creators, writers and producers who have tried to 'do the right thing' for audiences. There are interviews with Hugh Laurie (House), Alan Alda (Hawkeye in MASH), Gillian Anderson (Scully in The X-Files), Dennis Franz (Sipowicz in NYPD Blue) and Michael K Williams (Omar in The Wire). Show less