Who is Captain Walker, Major Townsend, the Chief of Staff from The Man with the Golden Gun and what is their importance?

These three characters are among the first who Bond encounters when he returns to London after being presumed dead. All three characters are suspicious of his changed manner, and indeed of his unexpected return. All three grudgingly accept who he is but with reservations and suspicions. Those suspicions are proved correct when Bond attempts to assassinate M, his boss.