[Polybius]

Mrs Blair, a staunch Catholic, chose to exercise the "privilege du blanc", usually granted only to the wives of Catholic monarchs.

Well, she is Catholic and she is the British equivalent of "First Lady", so, that seems to be the modern day equivalent of a "Catholic Queen".

The bottom line is that her pillow talk is more politically powerful than Prince Phillip's pillow talk.

[Oztrich Boy]

Well, she is Catholic and she is the British equivalent of "First Lady",

No she isn't, She's just a lawyer with delusions of granduer.

[Conservative til I die]

Well, she is Catholic and she is the British equivalent of "First Lady", so, that seems to be the modern day equivalent of a "Catholic Queen".

Actually, when they say "Catholic Queen" they mean it literally, since the "modern day equivalent" of a Catholic queen is actually a Catholic queen (several of them).