Google has added a profile of the Queen's head to its homepage logo in honour of the monarch’s visit to its London office today. A crown sits atop the logo's 'e'.

'Google Doodles' on the internet giant's search engine homepage change occasionally to mark holidays, birthdays of famous people, and major events, such as the Olympics.

Wikipedia states that the first Google Doodle was designed by Larry Page and Sergey Brin to notify users of their absence in case the servers crashed.

"Subsequent Google Doodles were designed by an outside contractor, until Larry and Sergey asked then-intern Dennis Hwang to design a logo for Bastille Day in 2000. Hwang has been designing the Google Doodles ever since.

"Clicking on a Google Doodle links to a string of Google search results about the topic.

"Google doodles have been produced for the birthdays of several noted artists and scientists, including Andy Warhol, Albert Einstein, Leonardo da Vinci, Louis Braille, Percival Lowell, Edvard Munch, Béla Bartók among others.

"The celebration of historical events is another common topic of Google Doodles including a Lego brick design in celebration of the interlocking Lego block's 50th anniversary."

According to the BBC, the Queen and the Duke of Edinburgh will meet staff, young 'Doodle' competition winners, and users of Google’s YouTube - the Queen has her own royal channel on the popular video site.

The royal pair will also meet Nikesh Arora, the president of Google's Europe, Middle East and Africa operations.

They will be shown Google's various operations, and will meet schoolchildren who won a competition to design new 'doodles'.

PC Advisor visited Google’s HQ yesterday, and saw the winning children's Google doodles.