It is also soft and foldable, "Constructed to fold flat when not in use ..."[1] The Canterbury cap is the medieval biretta, descended from the ancient pileus headcovering.
[citation needed] In Anglican churches, clergy are entitled to wear the cap, which is worn for processions and when seated to listen to Scripture or to give a homily, but not when at the Holy Table.
It has gone through several modifications: once of the comely shape that we see in the portraits of Bishop Fox and others, it developed in the seventeenth century into the form sometimes called the Canterbury cap (of limp material, with a tuft on the top), and then into the still beautiful college-cap in England, and abroad into the positively ugly biretta.
There is no conceivable reason for English churchmen to discard their own shape in favour of a foreign one, except that the biretta offends an immense number of excellent lay folk, and thus makes the recovery of the Church more difficult.
[1][failed verification] In the Catholic Church, its use is identical to that of the modern biretta, into which, on the continent, the cap evolved into throughout the centuries.