Thanks John and sorry about the link. I will try again below.
http://www.thames.org.uk/pages/massey.htmlThere are few mentions of this meeting, so I guess it wasn't that secret after all, unless all the references are from a single source that is wrong.
A better link is at
http://www.adls.org.uk/shipinfo.cfm?id=55&RestTrust=0which has the following:
QUOTE
In 1947 her original open canvas dodger and screen were replaced with a purpose-built enclosed timber wheelhouse. Another claim to fame came in this year when a secret meeting in the Thames Estuary between Herbert Morrison (Member of Parliament and Chairman of the London County Council) and Aneurin Bevin, MP eventually resulted in the formation of the National Health Service.
A side note on the boat itself. It has a claim to fame for being at Dunkirk, not to put out fires, (it was a London Fire Brigade boat and so under Morrison's control), but to ferry troops off the beaches.
Also in the above quote Bevin should read Bevan.
1947 would have been the year before the National Health Service act. Maybe the oposition of the BMA was scaring some of the cabinet ministers, but still Nye Bevan and Herbert Morrison seem strange bedfellows. I was hoping that one of them would have mentioned it in biographys or such like. Much later, after Atlee retired, Morrison does say that he and Bevan had made a deal for him to become leader in the leadership election which Gaitskell won. I'm guessing Gaitskell was further to the right than Morrison.
Today it's hard to decide what is the right of Labour Party as I heard Tony Benn saying that even Ted Heath was to the left of Tony Blair.

If we think of Morrison and Ernie Bevin being on the right of the post war party, by today's Labour Party standards they would be extreme left.
I suspect the CIA didn't need to do much with the leading Labour figures as they were strongly anti-Russian anyway, certainly Bevin wasn't wanting to give an inch in the post-war carve-up.
I think if the meeting did take place you are pointing me in the correct direction. Maybe Morrison was trading his support for the National Health Service for future support from the left in any leadership battle. If for any reason Atlee hadn't completed his full term then the fight might have been between Morrison and Ernie Bevin, both of the right, with Nye Bevan and the left being the swing vote.
If, and I might have this totally wrong, Morrison was having an affair with Ellen Wilkinson, would this have made him more acceptable to the left? She died in February 1947 so the date of the meeting could be interesting.
Last note and going back to the quote above, in more than one reference the meeting was said to be in the Thames estuary, that is the boat actually put out in the river and it wasn't just a fleeting visit to a tied up fire boat.
Thanks again for anyone who can dig up something on this meeting.
Danny