Rrerku

I graduated last year from a master's course where I was fortunate enough to top the cohort. However I was told this in confidence by one of my referees to a PhD programme, and they informed me that under no circumstances was I to put this on academic applications, as it would be against 'department guidelines'.

I also tried to enquire with the department directly concerning class rankings, but as expected they were unwilling to reveal this information to me.

I'm now considering applying for a job in the 'real world', and believe that the class ranking would be a good thing for my CV. However I really ought not to know this fact, as it was revealed to me in confidence by my referee, and I risk jeopardising my relationship with him if the department found out.

Am I overthinking this, and should I just put it down, or is there a way to resolve this in a less risky way?

So, you put it on your CV, the future employer does what employers do and phones the institution to check details of awards, years etc.

BOOM - the institution does not confirm you were "top of the class" as that is just not done.

Now the future employer is confused - what else may be wrong on your CV AND your referee is pissed at you as well.

Do you really want to go there?

Aside from the insightful advice given by Solar Mike, I'd like to emphasize the importance of maintaining a good professional relationship with that referee. You would be compromising a seemingly valuable relationship by doing something he explicitly advised you against, and he will most likely include that information in some form in the letter/recommendation anyway. It is quite common for academic referees to state in their reference letters that the student is among top students in the course/class/whatever, for example, along the lines of "This student was among top 1% of students in the class". They have different ways and means of saying that, and I would trust that they know how to provide an excellent reference for an excellent student (it's an integral part of their job, after all). He trusted you, why wouldn't you trust him?

An action you could do that might be less contentious is to state your GPA for the course, but then you might want to adjust your CV accordingly (e.g., you'd probably want to state that for other courses). You could ask your referee about what they think of stating the GPA.