According to figures released today, staff in some foreign embassies are alleged to have committed crimes which, were it not for immunity from prosecution, could have seen them behind bars. Shoplifting, drink-driving and traffic offences are the most common crimes though robbery, sexual assault, threatening to kill and the aforementioned human trafficking also appear in the list.
It's not down to lack of effort on the part of the police either - requests for diplomatic immunity to be waived have been refused by the government, though in 2002 Tony Blair intervened to force Colombia to waive the immunity of two men accused of murder. Expulsion is pretty much the only sanction that the British government have over errant diplomatic staff - between 1997 and 2007, seven Saudi diplomats were expelled after being accused of serious crimes.
A wide variety of embassies are named in the list, including Pakistan, Nigeria, Saudi Arabia and the US. Much to Boris Johnson's well-documented chagrin, the US doesn't appear to consider its relationship with us special enough to warrant paying the congestion charge; at the last count they owed around £3.8m and steadfastly claim that they're immune from what they define as a 'local tax' though the mayor did offer a retaliatory strike last year when he publicly expressed his disapproval of their shiny new embassy building.