Osmond's spells have been broken and his spirit Grimbald captured. He decides to release Oswald from the prison in the hope that together they may at last defeat Arthur.
The Britons march on the Saxon fortress, and are met by Oswald, who proposes the war be decided in single combat with Arthur. After a very close fight, in which the two magicians are also pitted against each other, Arthur finally succeeds in disarming Oswald, but grants him his life.
A consort of trumpets within, proclaiming Arthur's victory. While they sound, Arthur and Oswald seem to confer. Arthur commands Oswald to return to Saxony with his men. Emmeline is restored to Arthur. Merlin imprisons Osmond and proclaims the triumph of British sovereignty, faith and love. Merlin waves his wand; the scene changes, and discovers the British Ocean in a storm. Aeolus in a cloud above: Four Winds hanging, etc.
Ye blust'ring brethren of the skies,
Whose breath has ruffled all the wat'ry plain,
Retire, and let Britannia rise
In triumph o'er the main.
Serene and calm, and void of fear,
The Queen of Islands must appear.
Aeolus ascends, and the Four Winds fly off. The scene opens, and discovers a calm sea, to the end of the house. An island arises, to a soft tune; Britannia seated in the island, with fishermen at her feet, etc. The tune changes; the fisher men come ashore, and dance a while; after which, Pan and a Nereid come on the stage, and sing.Еще Henry Purcell