Garry, I'm surprised you did not know that, previously, the requirement of speaking English did not apply to those applying on the grounds of marriage to a UK citizen.
It is interesting to note that the USA is also considering bringing in something similar (they already 'test' ability to speak English to a certain degree, whether you might be British, Canadian, Irish, Oz or Kiwi being irrelevant) but they are going to bring in more thorough tests. When I posted on British Expats that I thought it was stupid to test native English speakers in English, the response from every single Brit was 'we don't mind, how do they know we speak good English?' Interesting that everyone on here seems up in arms about it. I personally agree that BOTH the US and UK (and Australia, Canada etc) should wave this test for citizens of English speaking countries by birth (not naturalised).
Of course a British person might only speak Welsh...
Incidentally, in the US, you actually have to have a face-to-face citizenship test and in talking to you the examiner can usually tell if you are 100% fluent in English and skip that part of the test. Some people on British Expats reported that this was what actually happened, one saying the examiner just said 'Obviously you speak and understand English...'
So maybe the answer would be to have person-to-person exams instead of doing everything by paper.