Your paper contract is what matters, not the opinion of your managers. Most contracts refer to (in the UK) the patent act of 1974 and specifically claims by an

Your paper contract is what matters, not the opinion of your managers. Most contracts refer to (in the UK) the patent act of 1974 and specifically claims by an employer against work are restricted to that which they ask you to do, that which they support you in doing (financially, or with time benefits). Anything outside of those fall within your own remit and providing it's happening without their asking you to do it, and without them paying you or giving you time to do it... then anything you do is outside of work in your own time and whatever your employer says has no bearing on this. Basically, they can control what you do at work and on their behalf... beyond that, they have zero say. If you want to stay where you are, engage a lawyer to have this conversation with them. I pretty much had to do the same with my last employer just to make it explicit that what I created in my own time was nothing to do with them and they have no say over.