A Very British Threesome [FFM] #NSFW

I’m a male in his mid 40s. Divorced. and have a fantastic new lady in my life who is in her mid 30s. Been dating for nearly three years, going really well and over our conversations she spoke about having nearly had a (FFM) threesome in her past. The thought excited her and we agreed it would be a fun relationship experiment to try and make it happen again, but properly.
I was TOTALLY up for it obviously, having never had one before, but at the same time I didn’t want to seem like I was pressuring her to do it. I wanted it to be HER project and that she had complete control over how and where and who etc. also the power of veto to pull the plug at anytime if she didn’t feel good about it.