What is the Polkey Deduction?

In Polkey v AE Dayton Services Ltd. [1987]  the House of Lords said that the compensatory award can be reduced or limited to reflect the fact that you would have been dismissed anyway and any procedural errors made by your employer would not have affected the outcome. This covers everything that your employer did in dismissing you such as suspension, your right to be accompanied, the disciplinary hearing etc. 

Note however, that the qu