Complex sentence: News that his long-pending application for British nationality had been granted reached him in France in late December and early in the 1949 he returned to London to swear the oath of allegiance to the British Crown.
Split into simpler sentences: News that his long-pending application for British nationality had been granted reached him in France in late December. Early in the new year (1949), he returned to London to swear the oath of allegiance to the British Crown.