The sentence is:
We apologise for the destruction of your property by our workers.
What would the "by our workers" part be called?
It seems similar to the passive sentence structure where "by our workers" would be the subject. But the "destruction of your property by our workers" is a phrase and not a sentence so I am not too sure. Could someone tell me what would the "by our workers" part be called?
Thanks
As you suspect, the by preposition phrase has the same sense it has in a passive clause.
Nouns can have complements just as verbs can—especially nouns which are derived from verbs. That sort of noun typically takes most of the same sorts of complements as the verb it is derived from.
In some cases the complement takes a different form. The Patient of a verb is typically expressed by an of preposition phrase with the derived noun, and the Agent subject of an active verb is expressed by a possessive with the derived noun:
... the workers destroy our property ...
↓
... the worker's destruction of our property ...
But this can also be cast in a sort of 'nominal passive': the Patient subject may be expressed either a possessive or an of preposition phrase, and the Agent is expressed the same way as it is with a verbal passive—with a by preposition phrase:
... our property is destroyed by the workers ...
↓
... our property's destruction by the workers ... or
... the destruction of our property by the workers ...
