London’s Scotland Yard, police HQ, gave President Barack Obama the codename ‘chalque’, which means ‘smart alec’ in Punjabi. 
The story was broken in the Daily Mail before Obama's arrival in Britain. A spokesperson from Scotland Yard maintained that the codename was chosen at random by a computer program.
However this was put into question when a Sikh commuinity newspaper reported that this word ‘chalque’ was used used to ‘denigrate’ someone.  This embarassing story was then picked up by Yahoo News and The Drudge Report. 
Asra Q. Nomani a journalist with The Daily Beast said that she found the word insulting and thought it described someone “who is a notch below diabolical”. She wanted to double check and consulted her mother who confirmed it is insulting and checked in the the dictionary where its definition reads: “adj. skilful; knowing; crafty; sly.”
The journalist concludes after some debate that Arnold Schwarzeneggar’s recent deceipt and Berne Madoff, who swindled millions out of foundations could both be reffered to as a chalque. 
Scotland Yard however insist that it was not the President directly who was being referred to as a ‘chalque’ but “operational name for the state visit”. They told the CBS News that there was not a lot of choice that went into the name. 
It was chosesn “in sequential order from a randomly selected list."
So it seems that the computer came up with this mildly insulting name for the dignitaries visit rather than the British police. 

Queen Elizabeth II and President Barack Obama prior to a dinner hosted by the queen, Tuesday, May 24, 2011, at Buckingham Palace in LondonAP