The German Chancellor Angela Merkel was given the red-carpet treatment on her one-day visit to London, addressing both Houses of Parliament in the Royal Gallery of the Palace of Westminster and taking tea with the Queen at Buckingham Palace, prompting one German reporter to remark that she was being received as "the Queen of Europe". See video >>
The cartoon by Paul Thomas from the Daily Express shows the Queen welcoming Mrs Merkel to Buckingham Palace. The Queen's husband, Prince Philip (aka the Duke of Edinburgh) stands nearby with a gag tied around his mouth.
Prince Philip is renowned for making verbal gaffes or clangers (see here for a 'best of'), so the Queen has gagged him to avoid him making any embarassing or offensive remarks to their important German visitor (like mentioning the war!)
Actually, Prince Philip is a member of the House of Schleswig-Holstein-Sonderburg-Glücksburg, a German ducal house, so he should feel at home with Frau Merkel.
• Bob cartoon (The Telegraph)