The St George's cross is to represent the age old ties with England and also because
Guernsey is a British Crown dependency.
The golden cross in the
national flag of Bailiwick of Guernsey is a part of the flag which was used in the Battle of Hastings by Duke William of Normandy.
The present
flag of Guernsey was officially hoisted in 1985 and the golden cross was added at this time to make the flag different from the English one.