How do I remove the externals propery of a folder in an SVN branch but retain the files?

Question

I have a branch in my SVN repo that has one folder with externals. I wish to remove the externals property from that folder but retain the files in the folder so that I can change them without affecting the original externals folder. How do I do that? If I simply remove the externals property with SVN command line or ToroiseSVN, the files get deleted in my branch folder.