Via a post on RASSF:
U.S. embassy owes a million pounds congestion charge
19 October 2006
LONDON: The U.S. Embassy in London owes more than a million pounds for the congestion charge in the capital, the mayor’s office said on Wednesday.
London authorities say the charge on driving in the centre of the city is a road toll and diplomats have to pay it like anyone else. Washington says it is a tax and diplomats are exempt.
The U.S. embassy has refused to pay the charge since July 2005. Several other embassies have also refused but London says the U.S. embassy is the worst offender by far.