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

Anticipatory it

482c

Anticipatory it makes forward reference to a complement clause, and may be used

to express impersonal agency:

The German reply was exactly what the Austrian government had wanted. 

It

was decided to issue an ultimatum to the Serbian government, framed in a

manner that would be likely to provoke war. 

It has been argued that rights are inevitably relative to each culture. 

Existential there

482d

Existential there allows an indefinite subject to be placed later in a passive clause.

This has the effect of creating greater focus on the passive subject:

There were

hundreds

killed in the earthquake.

(Note the word order. There were killed hundreds in the earthquake.)

I did complain, but 

there was

no action

taken at the time.