“Moreover, Lord Justice Arnold pointed out that the new copyright bar has been in place since 2009.”
A photograph of an out-of-copyright painting has no copyright of its own, so those images are public domain. UK museums have been selling “image licences” on them for more than a decade anyway. The Tate accepted the rule internally and kept claiming copyright in public. The National Gallery was even losing money on its licensing operation, so it charged scholars for the privilege of running a loss.