The British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa.
Learn is what linguists call a factive verb - it concedes no ambiguity. To learn something is to be absolutely certain of it.
Verbs and other predicates that are factive presuppose that the proposition they introduce is true. It could of course be the case that the speaker/writer is mistaken and the proposition is false -- but if the rules of English pragmatics are being followed, the speaker/writer uses a factive only when he or she is honestly convinced that the proposition is true.
By using learn, Bush was effectively saying 'The Brits have discovered that Saddam bought uranium, and Gosh Darnit I believe them!'.
Note: There is an alternative (and only slightly less worrying) explanation.
Non-factive verbs give the entity using them some leeway or wiggle-room.
A partial list: think, suppose, expect, allege, assume, believe, guess, maintain, believe, hazard.
Is it not strange that the two verbs most commonly used to describe the act of an IDP representing some set of a user's attributes to a relying party are claim and assert - both non-factive?
I see the lawyers at work
Your Honour, my client made it perfectly clear that they were only 'claiming' that the user had logged in. If the defendant chose to grant access to their resources based on my client's beliefs then surely my client cannot be held responsible.