It looks like the NPG asserts that use of the images is illegal, but isn't willing to sue the Wikimedia Foundation over it, so they're at something of a stalemate with Wikimedia de-facto winning (but with no guarantees for other parties who aren't Wikimedia). Wikimedia's official position seems to be more or less an ultimatum of, "these are public domain, sue us if you think we're wrong": http://commons.wikimedia.org/wiki/Commons:When_to_use_the_PD...
It looks like the NPG asserts that use of the images is illegal, but isn't willing to sue the Wikimedia Foundation over it, so they're at something of a stalemate with Wikimedia de-facto winning (but with no guarantees for other parties who aren't Wikimedia). Wikimedia's official position seems to be more or less an ultimatum of, "these are public domain, sue us if you think we're wrong": http://commons.wikimedia.org/wiki/Commons:When_to_use_the_PD...