Caratacus

Caratacus or Caratach was a first-century British chieftain of the Catuvellauni tribe, who led the British resistance to the Roman conquest in AD 50-51.

Caratacus' fighting technique included conventional battlefield warfare (which he was unsuccessful at) and guerrilla fighting (which he was successful at). After his final defeat (the site of which is lost to history) he fled to the territory of Queen Cartimandua, who captured him and handed him over to the Romans. He was sentenced to death as a military prisoner, but made a speech before his execution that persuaded the Emperor Claudius to spare him. He lived out the remainder of his life in Rome, and his death is unrecorded.

Caratacus in Ruled Britannia
Caratach was a character in William Shakespeare's Boudicca. He was the brother-in-law of Boudicca and commander of the Iceni army. He cautioned his cousin against underestimating the Roman legions and overextending her army, but his warnings fell on deaf ears. He was ultimately killed by Gaius Suetoniua Paulinus, but not before killing Marcus.

In the 1598 debut of Boudicca, Caratach was played by Richard Burbage.

Literary comment
OTL playwright John Fletcher (an occasional Shakespeare co-author) cast Caratach in his 1613 play Bonduca (sic) as the enforcer and relative of the title character. This is a blatant historical inaccuracy, as Caratacus was exiled from Britain nearly a decade before the Iceni revolt, and there is no evidence that he ever had any personal connections or contact with Boudicca. In the afterward of Ruled Britannia, Harry Turtledove explains that he mostly cribbed his fictional play from that of Fletcher. However, in the novel itself, he mistakenly attributes Fletcher's inventions to Tacitus.

Caratacus does appear in an OTL Shakespeare play, in a fashion. Cymbeline is a play about Caratacus' father Cunobelin. The character Guiderius is a loose analog of Caractacus, however that play has even less connection to actual history that Fletcher's.