David Cameron will today roll out the red carpet for German Chancellor Angela Merkel, his best hope of winning concessions designed to satisfy eurosceptics within his own Conservative party.
Mrs Merkel is due to have lunch with the Prime Minister at Downing Street before meeting the Queen at Buckingham Palace.
She will also address MPs and peers in the Royal Gallery at the House of Lords.
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The pomp and circumstance surrounding her trip contrasts sharply with last month's visit by French leader Francois Hollande.
Instead of a meal at Downing Street, he and Mr Cameron instead plumped for a casual pub lunch in Oxfordshire.
However, in what will be seen as a blow to Mr Cameron, Mrs Merkel is also due to meet Labour leader Ed Miliband while she is in London.
Mr Cameron is keen to persuade Mrs Merkel to assist his campaign to renegotiate the UK's relationship with Europe ahead of his pledged 2017 In/Out referendum.
While the German leader is understood to be sympathetic to some of the Conservative Party leader's proposals, briefings from Berlin suggest that she is set to disappoint him on issues such as his call for a rethink on the free movement of people within the European Union.
Downing Street has said that the Prime Minister will use their talks to raise issues such as welfare tourism, economic competitiveness and deregulation.
They are also expected to discuss the ongoing situation in Ukraine.