Forking a repository that I have transferred

I transferred a repository to another account. The url of the old repository redirects to the new repository, which is good.

Now I want to fork the transferred repository to the old account, and I’m worried this will ruin the redirect. Presumably the url of the fork will be the same as the one I want redirected. If I had been able to rename the fork then presumably this would have solved my issue.

Anybody know how I could resolve this?