Another way to raise money for London would be getting foreign embassies to pay their parking fines...
A freedom of information release by Transport for London (TfL), responsible for the transport network in the city, found that the American embassy had accumulated debts of £14.6 million over 20 years, when the capital's congestion charge was brought in,, the most of any embassy in the U.K. capital, official figures show. (@VOX.com) The Japanese Embassy was second on the list, owing more than £10 million, while the Indian High Commission owed £8.5 million. Among all embassies, the total unpaid figure from 2003 to December last year was £143.5 million.
...a spokesman at the American Embassy says they're exempt according to the 1961 Vienna Convention on Diplomatic Relations but London transport retorts "the congestion charge is a charge for a service and not a tax. This means that diplomats are not exempt from paying it."