GUEST COMMENT: Unless you follow this advice, you will come to regret your exit interview

An exit interview seems like a riskless trade. A fifteen minute nirvana in which you get to vent your spleen after years of grovelling obeisance.

It may seem that there's limited downside to a frank and forthright exit interview. After all, you've already resigned. If you're going to a competitor, there's surely a limited amount the most vindictive manager can do to sabotage your prospects. If you're going to a client, your boss will be facing the prospect of a quite different dynamic the next time you meet across a mahogany table.

Even better, if you're off to set up an orphanage in Kenya or a smoothie business in High Street Ken, you're untouchable.

Or not.

In some cases, an exit interview is a totally pointless exercise. These will be the occasions

upon which it's conducted by an HR person with a degree in anthropology from Exeter University. In others, they will have lasting repercussions. These will be the cases upon which they're conducted by a line manager who will listen to what you say and faithfully relay the impact of the bombs you've dropped to your ex-colleagues.

Tempting as it may be to drop these bombs. you should do so with care. The City is a small place. You could end up jeopardising your career if you come up against one of the bombed colleagues in future.

There is an art to the exit interview. And it is this:

Never criticise someone without appearing, on the face of it, incredibly upbeat, positive and helpful.

For example, don't say: "X is frankly impossible to work with. He is an inept micro-manager who constantly changes priorities, knows absolutely nothing about the market and has lost us at least four clients over the past six months."

Do say: "This has been a brilliant place to work and I'm really regretting moving on. A few things could have made my time here better - X has a bit of a reputation for shifting priorities and on one occasion I had to try and patch things up with client Y, but overall it's been great."

Trust me. You can and must NEVER burn your bridges in the City of London. Plenty of people end up coming across the same boss twice. Never assume you won't be one of them.

The author works for an investment manager and has given up telling people how he sacrificed the best years of his life on the altar of investment banking.