I've tried deleting it from both the PC and the app but can't get it to go from either. The sticking point seems to be that the tab "Family Trees" on the top of my (PC) Ancestry Home page does not give the same drop down menu as per the instructions above.

I've not done anything with the app so far as I can't export my family tree( kept on my PC using the Family Tree Maker program) to the app and also want to remove the wretched interloper tree first as it gets in the way !