Which Byzantine guard did some English veterans of Hastings later join?

Some English veterans of Hastings later joined the Byzantine Varangian Guard.

The Varangian Guard was the elite bodyguard of the Byzantine emperors, based in Constantinople. It originally drew heavily on Scandinavian warriors, especially men connected with the eastern Viking world, but its character changed after the Norman Conquest of England.

Many English fighters lost land, status, or employment after William’s victory in 1066. Some sought careers abroad, travelling through Scandinavia and eastern Europe to Constantinople, where they could serve the Byzantine emperor as professional soldiers. Englishmen became an important part of the Guard from the late eleventh century onward.

The Guard was famous for loyalty, heavy weapons, and its large Danish-style axes. It was not the same as the Roman Praetorian Guard, the Swiss Guard, or a generic imperial guard. The connection with Hastings is best understood as part of a wider English exodus after the conquest; historians accept the migration and Byzantine service, although detailed stories about particular refugees are sometimes based on much later sources.