Complex sentence: He stayed on in the RAF, being promoted to full Squadron Leader on 1 August 1947, Wing Commander on 1 January 1953, and finally Group Captain on 1 January 1960.
Split into simpler sentences: He stayed on in the RAF, being promoted to full Squadron Leader on 1 August 1947. Promotion came twice more, to Wing Commander on 1 January 1953, and finally Group Captain on 1 January 1960.