At the time of their suppression, a small number of English and Welsh religious houses could trace their origins to Anglo-Saxon or Celtic foundations before the Norman Conquest, but the overwhelming majority of the 625 monastic communities dissolved by Henry VIII had developed in the wave of monastic enthusiasm that had swept western Christendom in the 11th and 12th centuries. Few English houses had been founded later than the end of the 13th century; the most recent foundation of those suppressed was the Bridgettine nunnery of Syon Abbey founded in 1415. (Syon was also the only suppressed community to maintain an unbroken continuity in exile; its nuns returned to England in 1861.)