Cinderella had very small feet. This fact is rarely mentioned in the telling of the story but it is the only logical explanation. If her feet were average size then the glass slippers would have fitted most young women who tied them on. Of course it could be that Prince Charming knew all along who his attractive and mysterious dance partner was. The "who so ever these slippers fit I shall marry" proclamation would be a lot less risky if the feat were exceptionally dainty and he knew who they belonged to. It's much the same with recruitment.
If you have three internal candidates for the newly created post in the latest restructuring what better way of ensuring you get Cinderella and not one of her equally well qualified but less attractive sisters than by putting the shoe size into the person specification. Strictly speaking it's hard to argue a case that the right size feet are an essential requirement, being a good dancer would be easier to justify but then again this might open it up to the other two.
It is not just internal appointments where this sort of adjusting the person specification to fit the preferred candidate goes on. I can't be the only person to have been told in feedback that I did a good interview but the other person was a "better fit". Sometimes that better fit may be in terms of gender or race which of course could never be explicitly stated or simply we like the one we know but HR made us advertise the post / hold competitive interviews.
From the point of view of the candidate if you get an interview you're in with a chance. As an experienced interviewer I know how many times someone who looks good on paper is a disappointment in the interview and on many occasions I have witnessed the favored candidate be put into the shade by someone who can offer something different. All of which reinforces the importance of ensuring the person specification does not contain unnecessary "silver slipper" requirements as essential criteria for interview. Managers may draw up the person specification but best practice involves a robust review of the essential requirements by HR. This reduces the risk but is no guarantee against a partially devious manager.
As a senior manager I heard an appeal by an employee who claimed she had been deliberately excluded from applying for a post by a manager introducing an essential requirement into the person specification at the last moment. The additional requirement was supervisory experience even though this was a first line manager post so would not normally require previous management experience. The manager had successful argued with HR that this post was an exception as it was a new role and a pilot which if success full would be rolled out a cross the department and in recognition of this he was proposing to offer the successful candidate a starting salary at the mid band point. All of which sounded very plausible until you took into account the fact that the employee was black and that the person specification was changed after the manager got wind she was intending to apply.
If the shoe fits!
Blair McPherson author of An Elephant in the Room about equality and diversity in the public sector published by Russell House www.blairmcpherson.co.uk