It's called a compromise agreement and is a valid way to pay financial compensation to someone to leave a role without pursuing a misconduct or redundancy option.
You can negotiate the amount and £10,000 may have been a starting offer, however if the company is prepared to pay then you are entitled to ensure the agreement includes clauses such as a recognised reference wording and you can choose how it is communicated why you have left. You also have to be given independent legal advice.
You leave with a clean record and with money in your pocket with confidentiality for both sides.
Also the fact that a compromise agreement has been discussed can't be used against either side in the main part. Therefore not blackmail at all, but still not nice if you weren't expecting it.
Biting the hand that feeds IT
