I don't think Ken Livingstone should be left out when it come to making out views felt about this kind of nonsense. Especially by Americans and other swho mioght feel that this is a reason to go to other capital cities when on their travels.

Here is an extract from the relevant website for the London Mayor:

Getting in touch by letter or telephone The address of the Mayor and Assembly is:

Romney House
43 Marsham Street
London SW1P 3PY
Tel: 020 7983 4000
Minicom: 020 7983 4458

Hours of operation will be between 0830 to 1800 Monday to Friday.

Getting in touch by email
If you have a question that you wish to raise with the Mayor, you should send your correspondence to:

mayor@london.gov.uk

Getting in touch by fax
Fax number: 020 7983 4057