Why diplomatic failure is not always an ambassador's failure

Can you give examples of some of the worst British ambassadors in history?

No individual is selected. The difficulty is separating an ambassador's mistakes from a government that gives poor direction or ignores accurate warnings, as in the example of Argentina and Port Stanley.

A failed policy does not identify where the failure occurred. Some unsuccessful ambassadors disappear from public view because they are quietly removed, while others can receive poor information or direction from their government. The example of Argentina and officials in Port Stanley raises a different problem: warnings can reach London and still receive no attention. In that case, blaming the diplomat for the eventual crisis would miss the ministers who refused to act.