Ok, I don't know if there is a loophole currently, but there WILL be if the GRA goes through as it is currently proposed. Dr Nicola Williams from Fair Play For Women describes it very well in her talk at LAWS Plymouth: m.youtube.com/watch?v=NqxzLy0O-4E# - from around 30mins. This is because of the proposed right to secrecy about previous names.
As someone who has had to require checks for employees (the old CRB at the time), I'm absolutely horrified by this idiotic idea, particularly given that it's such a double standard - children sitting GCSE and A-levels had to declare their legal name (last year at least but I wasn't informed that had changed this year), not their "known by" name. The school I worked at last year flipped out as this could have revealed children who were at risk if their real names were known.