Armstrong was knighted in 1958 and retired in 1968, when he was 70. He and his wife moved to the village of Newton Blossomville in Buckinghamshire, close to the Bedfordshire border. There he formed and conducted a village choir, which won several prizes in music festivals. After the death of his wife in 1982, he moved to Olney, a few miles away, sharing a cottage with Rosemary Rapaport, his former colleague from the RAM. Robert Armstrong recalled that in Olney, when already ninety years old, Armstrong "was delighted to be sought out, as 'the old man in East Street who plays the organ', to play for Mass at the local Roman Catholic church for six months."