"the Grecian tents where Cressid lay that night"
'Cressida' by Poynter (1888)
Public Domain Cressida (1888) - Credit: Edward John Poynter (1836-1919)

Cressid, often written Cressida, Cresseid or Criseyde, first appeared in a work by the 12th Century poet Benoît de Sainte-Maure.

A young Trojan woman living during the Siege of Troy, she is in love with Troilus, the youngest son of King Priam. But whilst a hostage in the hands of the Greeks, she is seduced by Diomedes, a Greek warrior.

The story was retold by Chaucer in Troilus and Criseyde, and by Shakespeare in Troilus and Cressida.

Cressida is sometimes seen as symbolising inconstancy in love. Whether Waugh wishes us to equate Julia with Cressida is not clear.