Troilus and Cressida
Role: Patroclus and Troilus

Jeremy played Patroclus in his debut with The Old Vic. Later, he graduated to the title role of Troilus, opposite Rosemary Harris as Cressida.

Troilus and Cressida is a satiric tragedy by William Shakespeare, set during the Trojan War between Troy and Greece. Troilus is a prince of Troy, a warrior and honorable man. He is desperately in love with Cressida, a beautiful young Trojan woman. Patroclus, the other character Jeremy played, is a Greek warrior, Achilles' best friend -- and, it is suggested, his lover. 

The Old Vic staging of Troilus, directed by Tyrone Guthrie, moved the action from ancient Greece to pre-WWI Europe, with the characters in Edwardian costume. The Trojans were dressed as British Life Guards and the Greeks as the Kaiser's Prussians. 

About the production, from 
Troilus and Cressida in Performance:  

One of the most influential stagings opened in 1956 when Tyrone Guthrie directed it at The Old Vic. John Neville and Rosemary Harris played Troilus and Cressida, Wendy Hiller was Helen, John Wood played Helenus, and Jeremy Brett Patroclus. ... The Greeks were uniformed as pre-WWI Germans or Austrians, while the Trojans were in a more fanciful version of the same era. Though many critics complained of Guthrie's playful excesses, Kenneth Tynan claimed that he "made Troilus and Cressida seem like a new play." 

Review of the Broadway production, 
from Time magazine:

Troilus is a difficult as well as an imperfect play. ... Shakespeare's narrative recounts the harlotry of love and the homosexuality of friendship, shows war grotesquely fumbled and honor traduced. ... All the more to enforce the prevailing decadence, Shakespeare provides a simple and trusting Troilus (who is soon betrayed), a manly and serious Hector (who is ultimately butchered). ...

In staging this Old Vic's Troilus, Tyrone Guthrie has swept the décor and atmosphere of the play some 30 centuries forward. He has boldly evoked an Edwardian world full of prance and panoply, his Trojans very British, his Greeks very German.

The Old Vic company gave 14 performances of this play at the Winter Garden Theatre from Dec. 26, 1956, to Jan. 12, 1957, according to the Internet Broadway Database.

New York Times reviewer Brooks Atkinson found Guthrie's staging to be awkward, but heaped praise upon the actors:

When the actors have a moment to act the drama they are excellent. ... Jeremy Brett's youthful, eager Troilus who can hardly believe Cressida's treachery -- is a first-rate bit of straightforward acting. 

The International News Service called the production "a tremendous spectacle of lust and warfare":

War in Edward's time was still a sport as it was in the days when the young Trojan warrior Troilus sought revenge on the Greeks who had stolen and corrupted his love, the fickle Cressida. ...

Troilus as played by Jeremy Brett was stalwart, anguished and handsome.

Above, Jeremy Brett as Troilus and Rosemary Harris as Cressida.

Jeremy's performance earned him an award for Most Promising Actor of 1956. 

Plot summary // Full text of play

Below, a Hirschfeld caricature of Jeremy Brett and Rosemary Harris in Troilus and Cressida. Click for the full version, with the rest of the cast.

From the early performances in England comes the photo below, of Jeremy, at left, as Patroclus; Richard Wordsworth as Ulysses; and Charles Gray, at right, as Achilles. (Charles Gray would go on to play Mycroft Holmes, brother to Jeremy's Sherlock in the Grenada productions.)

Audio recording 
1961 
Role: Troilus

Audio/video clip from Troylus & Cressida 

From Troilus and Cressida in Performance: 

In 1961, Howard Sackler assembled one of the best casts ever to undertake the play for the Caedmon audio recording. As the lovers, he had Jeremy Brett and Diane Cilento. 

Alan Howard, who would later play Achilles at Stratford, played Hector on the recording and the brilliant Irish character actor Cyril Cusack played a bitter snarling Thersites. Max Adrian's Pandarus was saved for posterity at least on vinyl. Patricia Routledge was Helen. Derek Godfrey, Peter Bayliss, and Alec McCowen played the Greek heroes Achilles, Ajax, and Diomedes. Eric Porter, who had played Ulysses for Hall and Burton at Stratford, returned to the role for the recording.