On the surface, a state visit is all pomp and circumstance, feel-good, made-for-the-camera moments featuring glamorous royalty, smartly-dressed soldiers and happy schoolchildren waving flags.
But Queen Elizabeth II is actually Britain's greatest diplomatic trump card – and Prime Minister David Cameron has chosen to play her in Germany at a time when he needs Anglo-German co-operation to be as strong as possible.
Later this week, he and Chancellor Angela Merkel will meet other European leaders in Brussels.
At the summit, the Prime Minister will broach for the first time just what it is that he wants to renegotiate with the EU before the British people vote on their membership in a referendum in 2016 or 2017.
Cameron has been backed into a corner over the referendum, forced to offer it as a sop to Eurosceptics in his own Conservative party and to avoid losing too many votes to the right-wing populist UK Independence Party.
Although she has plenty of other plates in the air, Chancellor Merkel has shown herself to be at least slightly receptive to his ideas.
At a preliminary meeting just a few weeks ago, she said she was happy for the UK to formalize its place in a "multi-speed Europe".
She even said that she might countenance changing the European treaties if that's what it takes to keep the UK in the fold.
“Where there's a will, there's a way,” was the killer quote that cheered Cameron and other British observers hoping for co-operation from the “Queen of Europe”.
After that meeting, Cameron said that he had “every confidence” of getting what he wanted out of his planned EU renegotiation.
But it hasn't stopped Eurosceptic members of his party from kicking up a fuss over exactly how the referendum will be organized and how much anti-EU ministers or the largely pro-EU civil service will be allowed to talk about the subject in the run-up to the vote.
So the opportunity to chat with Merkel around the dinner table Wednesday evening in Schloss Bellevue, at an opulent state banquet hosted by President Joachim Gauck, is particularly valuable for the British leader.
That precious one-on-one time with the Chancellor is something Cameron could only have bought himself at the price of a state visit from the world's most recognizable public figure.
Although his reception in neighbouring France and Poland on the same trip was significantly frostier, Germany is seen by the UK as the potential core of a group of friendly northern EU states.
Along with the Danes, who recently elected a centre-right government of their own, Cameron believes the UK and Germany can bring together the EU nations who are more interested in trade than propping up weaker neighbours and political integration.
So behind the royal visit – with all its attendant media froth of olde-worlde etiquette guides and loving looks back at previous times the Queen has set foot in a country that was once a bitter enemy – is a charm offensive that almost no country on Earth can equal.
“The British Queen stands for Great Britain like no other person,” Merkel said on Friday.
No other country - or at least, no other country with the same global clout as the UK with its UN security council seat, top economy and status as one of the three largest European nations - can send such a well-loved symbol to another nation.
And the trip is particularly significant as, after 63 years and nearing her 90th birthday, the Queen's career of flying the flag abroad to support British interests draws to a close.
Many royal-watchers see this visit to Germany as possibly the very last trip overseas that the Queen will make as she gradually reduces her royal duties.
But we'll never know just whether the Queen herself has weighed in on behalf of the Prime Minister in her private conversations with Angela Merkel.
“In the 60 years that the Queen has been in office, nothing has ever emerged from conversations that she's held,” German government spokesman Steffen Seibert said before the monarch's arrival.
“That will of course also not happen when she comes to Berlin.”