I'm still unsure if we're talking about the same thing. My ipad is in a case like this:

Removing it and reinserting it is like this:
I use this case because of hand disabilities. What you're, and other posters, are saying, is that I have to pry the whole thing apart just to go through security, and then put it all back together again on the other side (something I cannot do without assistance.) Is this what you mean by "must be out of cases"? It means I have to find another case which works for my disability, and is easy to remove and reinsert the ipad. I wonder if such a case exists?

At CPH they did not have a problem with that case. Why is LHR different?