Well, the photo that Bryan's link uncovers (in more senses than one) opens up a whole branch of this investigation. With what Bryan's photo reveals (in more senses than one) we are given clues that can lead to the formation of a perfectly believeable hypothesis. The first three come from Bryan, the remainder from my own researches and I will give them sequentially:-

Fact 1 - Christine Keeler is photographed sitting back-to-front in the approved Critics Group manner.
Fact 2 - She appears to be wearing no clothes in the photograph. A careful study of the photo will show that this includes a complete lack of trousers.
Fact 3 - In the second of Lewis Morley's photographs on Bryan's link, Ms. Keller is off the chair and is clothed. However, even when she considers herself fully dressed, she totally eschews the wearing of trousers.
Fact 4 - Previous investigation on my part posted on this thread (13 Jan 12 - 01:08 PM) confirms that Ewan MacColl himself was very keen to get his trousers off.
Fact 5 - Like Ms. Keeler MacColl favoured not just a lack of trousers, but total nudity. The most telling evidence for this comes on MacColl's singing of Tam Lin where at one point he is shape -changed into "a mither-naked man.
Fact 5 - For those who consider that the previous five facts may just be coincidence, here is the most telling fact of all. Amongst the many fine songs recorded by the American singer, Phil Ochs were his own composition, "Christine Keeler" and MacColl's "Ballad of a Carpenter" those proving a close link between the two people under investigation.

I think that the evidence given above is enough to prove Bryan's theory that -
* Christine Keeler was a member of The Critics Group.
but I think we have also proved my suggestion that -
* Not every member of the Critics Group wore trousers to all their meetings.

I believe that before this investigation is concluded, we will be able also to prove MacColl's link to Stephen Ward, John Profumo, Mandy-Rice Davies, Lord Astor, Rachman and the whole of the Cliveden set.

Perhaps one of MacColl's supporters will pop up here to deny all of this - to which I will be able to answer, ""Well, he would say that, wouldn't he?"