Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

THE BE-PASSIVE: FORMATION

478

The be-passive is formed by making the object of an action or event the

grammatical subject of the clause and by using auxiliary be + the -ed participle

(ed-p) of the verb. 

The agent may be realised as a prepositional phrase, most typically with by

(

Û

481 below

):

subject

verb

object

Active: A police patrol | spotted | a suspicious vehicle.

subject

be + ed-p

agent phrase

Passive: A suspicious vehicle | was spotted | by a police patrol.

Be

-passives are different from lexical verb be plus -ed form adjectives, which

cannot normally have an agent phrase, and which may have particular

prepositional structures following them:

I’m 

worried about my mother.

(-ed form adjective)

(I’m worried by my mother.)