Gisa was born in Lorraine,[1] probably the village of St Trond in modern Belgium,[2] and was among a number of foreign churchmen brought to England by King Edward the Confessor.

[3] He went to Rome for consecration because the current Archbishop of Canterbury was Stigand, whom successive popes had excommunicated for various irregularities,[5] and travelled in company with another bishop—Walter of Lorraine, the Bishop of Hereford-elect—and Tostig Godwinson.

[8] He constructed cloisters to the north of Wells Cathedral and communal buildings to the south for the canons.

After the Norman Conquest, he introduced the veneration of new saints into his cathedral, as well as setting up an archdeacon in the diocese for the first time.

[8] He worked to restore lands formerly held by the bishop or cathedral that had been unjustly acquired by others.