The earliest clear mention of him dates from 1205 by which time he was already and canon, deacon and school master ("Magister Walterus") at the Cathedral of Our Lady.
He had received his own early education at the cathedral's chapter school, before going away to complete his studies in Theology at the newly founded College of Sorbonne in Paris.
[3] Between 1226 and 1229 Bishop Marvis was active in support of the pope's intensifying struggle against Catharism, and in 1233 he participated at the Council of Béziers as a Legate of the Holy See.
[4] During the years that followed his work, always in the service of the pope, was focused on his own diocese in West Flanders, which was undergoing a period of repaid economic development.
In these regions progress was being made with draining and ditching the land, opening the way to more intensive patterns of agriculture, able to drive and support the expansion of the villages.