The Byzantine Emperor Manuel I Komnenos, who had already entertained Louis VII in Constantinople at Christmas 1147 during the Second Crusade, was perhaps finally convinced by Philip that France would be a desirable ally in Western Europe.

Over the winter of 1178-1179 an Imperial embassy accompanying Philip, and led by the Genoese Baldovino Guercio,[4] was sent to the French court to secure a match between Agnes and Alexios, the only son and heir apparent of Manuel by his second wife Maria of Antioch.

[6] On arrival in Constantinople in late summer 1179 Agnes was met by seventy high-ranking ladies[7] and lavish festivities were organized for her.

[10] However, William of Tyre, who was present at the ceremony, seems to describe it as a full wedding (matrimonii legibus ... copulare); in this he is followed by some other non-Byzantine sources and by many modern authors.

[12] This ceremony came approximately one month after the wedding of Alexios' half-sister Maria Porphyrogenita to Renier of Montferrat, conducted by the Patriarch of Constantinople, Theodosios.

He was too young to rule unaided; his mother, Maria of Antioch, exercised more influence in affairs of state than Alexios or Anna.

In an attempt to escape the popular uprising that ended his rule, Andronikos fled from Constantinople with Anna and his mistress (known only as Maraptike).

Anna survived Andronikos' fall and is next heard of in 1193, when she is said by a Western chronicler to have become the lover of Theodore Branas,[15] a military leader who fought on the Empire's northern frontier.

Anna and Theodore eventually married, at the urging of the Latin emperor Baldwin I of Constantinople, in summer 1204.

[16] Theodore Branas continued to fight for the Latin Empire, and is last heard of in 1219, by which time Agnes has already disappeared from the historical record.