Barack Obama is expected to give deliver an upbeat speech to both houses of parliament on relations between the US and Britain.
But what about the actual hard politics going on behind the scenes?
Political editor Nick Robinson says some are claiming a new bond between the leaders, with personal chemistry over table tennis and assurances that they see eye-to-eye on the Arab Spring.
The critical issues, however, are the conflicts in Libya and Afghanistan - where in the former Whitehall is "un-nerved" by Obama's desire to keep a low profile while, in the latter, the US is concerned over UK promises to withdraw.
"The test will come of course, not in the words they use, nor even the hi-fives they give one another, but in the decisions they take when, if, the going gets tough in Libya or Afghanistan," he explained.
Foreign Secretary William Hague, however, disagreed with the premise that the US was not involved in Libya.
The initial Nato operation would have been impossible without US involvement, and a quarter of Nato sorties over Libya are US flights, he said.
"I make no criticism of the US. They are looking to allies to do a lot of this [the mission in Libya]."
Mr Hague was asked if the UK could be drawn into an Iraq-like quagmire if the Gaddafi regime collapses.
"It's very different from Iraq," he said, because of the lack of coalition forces on the ground, but it was right to point to the need for a blueprint for a political process.
Post-Gaddafi Libya "is something for which Libyans need to take prime responsibility," he added.
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