Past Perfect

FORMA

O Past Perfect é formado pelo verbo auxiliar "have" no passado (had) e o Past Participle do verbo principal.

Ex.: Thomas had been terribly disappointed when he met her.

Forma Afirmativa:

When I arrived there, I saw that I had gone to the wrong place.
They had lived in the same building for two years and didn't know each other.

Forma Interrogativa

Had you been there before?

Had I worked with them?

Forma Negativa

I hadn't seen them until then.

Hugh hadn't realized that the situation was so serious.

USO

Em um contexto já situado no passado, usamos o Past Perfect para mostrar que a ação à qual nos referimos é anterior às que acontecem no texto.

Ex.: I was talking to her, and suddenly, I realized that we had met once before.

Note que o Past Perfect deve estar sempre inserido em um contexto já no passado, ou sua utilização estará errada.

Fonte: Brasil Escola