But in an old man who has known human joys and sorrows, and has achieved whatever work it was in him to do, the fear of death is somewhat abject and ignoble. (Bertrand Russell How to grow old from Portraits from Memory; emphasis mine)
What is the purpose of the structure "it was" in the sentence? Does "it" refers to "work"?
How does the sentence compare to the following formulations? (Are they correct? Why? How are they different from the original sentence?)
- has achieved whatever work was in him to do
- has achieved whatever work in him to do