I recently praised another excellent adaptation of a Trollope novel, The Way We Live Now, and while He Knew He Was Right is second to that one, Bill Nighy's sleazy, cunning, charming and incredibly small performance (he's only in a few short scenes), is enough to recommend this.
Poor Louis is a man plagued by the rules of proper English society in the 1868. Eventually the vaguest hint of impropriety leads to jealousy, which leads to obsession, which leads to insanity, which leads to death. Is it too awful that the character is so miserable at by the end I just can't wait for him to die? Still, I'm making this sound much more horridly morbid than it is.
The supporting plot lines and characters offer sweet comic relief and spells of true romance. Like his other works, there are many men and women trying to cope with the various hassles of living in such changing times, and all their stories give a truly interesting insight to a unique period in history.
And Bill Nighy, honestly, you could just watch it for the twitch of his head.