Behalf: Realisation & WH– Probe

Halliday & Matthiessen (2014: 322):

Expressions of Behalf represent the entity, typically a person, on whose behalf or for whose sake the action is undertaken — who it is for.  They are expressed by a prepositional phrase with for or a complex preposition such as for the sake of, in favour of (negative: against), on behalf of … The usual interrogative is who for?.