Anna, has it gone because you have done something, or because you've managed to clear your conscience?
There's a question

Makes me think I'm back in the Counselling chair at Charing Cross again

And of course it's me so there ain't gonna be a quick and simple answer is there

It's both of those things. Done something - yes I have and it has given a nice little dose of release whether what I've done has value or significance is irrelevant. Cleared conscience - Yes. In the far, deep background I've felt guilty about knowing this for 25 odd years. I don't anymore.
But the biggest reason it's gone is something else which I'll try and get across, bear with me if I don't get it quite right.
Growing up I went through the whole Scouts thing: Cubs, Scouts, Venture Scouts: all the way, every award, badge whatever. It was the best thing that could have happened to me. It instilled a sense of Duty to others. To do your best for other people. It's there in the scouts promise. And for me that's still a truth. Doesn't matter how trivial or important what you can do is, all that matters is that you do your Duty to other people. I guess another way of saying it might be "We are in this together". All of that was reinforced by the world I grew up in with a strong self-reliant and supportive community. All this time I've not kept my promise to other people and that's whats gnawed away - I'd not done my duty. Sounds trite but I'm trying to encapsulate something a bit elusive.
Anyhow that's what really powered the flick that sent that ugly gibbering fucker spinning off my shoulder back to where it came from