THE Commission appointed to advise on the choice of a church to serve temporarily as the cathedral of the new diocese of Portsmouth has a delicate task before it. That of St. Thomas of Canterbury, the parish church of Portsmouth, was weak enough, except on historical grounds, for the church accommodates only 700 and is actually still pew-rented. St. Mary’s, Portsea, is dignified and spacious. But there are cogent reasons against the choice of St. Mary’s, though it has long been considered to have the reversion to the title. Rivalries would disappear, and Portsmouth would share the experience of Truro and Liverpool that the building of a cathedral welds a new diocese into its proper unity.