"had already been done" is correct and usable in written English. You can use this phrase to indicate that something happened before the present moment in time. For example: "The project had already been done by the time she arrived."
But the damage had already been done.
The damage, however, had already been done.
The talking had already been done.
That had already been done.
But the deal had already been done.
The damage had already been done, though.
Still, much damage had already been done.
The damage had already been done.
But the political damage had already been done.
The damage to public confidence, however, had already been done.
By then, the damage had already been done.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union