Catuvellauni, probably the most powerful Belgic tribe in ancient Britain; it occupied the area directly north of the River Thames. The first capital of the Catuvellauni was located near Wheathampstead, but after their defeat by Julius Caesar in 54 bc, they expanded to the north and northwest, building a new capital at Verulamium, near St. Albans. The Catuvellauni practiced agriculture extensively and apparently had a prosperous economy.