Complex sentence: The individual will sit on the Executive Committee of the Army Board (ECAB), Army Board and work with the Secretary of State for Defence, top civil servants and other high-ranking members to shape British Army policy.
Split into simpler sentences: The individual will sit on the Executive Committee of the Army Board (ECAB) and the Army Board. They will work with the Secretary of State for Defence, top civil servants and other high-ranking members to shape British Army policy.