[stan_rogers]

Knighthood is a life award. You are given the rank of Knight Commander of an appropriate order or made a Knight Bachelor (no particular order; lower precedence when it comes to deciding who walks in front of whom). The knighthood dies with the knight. Again, the "Sir" attaches to the given name ("first" name, even if that comes last or somewhere in the middle, or is a compound name in itself). In general, the "Sir" is only used for address or casual reference; you'd use the post-nominal letters in a more formal written setting.