I realise that the nuances of British constitutional arrangements are not a matter close to American hearts, but the Right Honourable (note correct spelling!) Lord Mayor of London is not the Mayor of London. The Lord Mayor is Mayor of the City of London, the financial district (aka ‘the Square Mile’). Like the City of Westminster, this is but a small area of the great city (with a small ‘c’) that is London. Surprisingly, the Wikipedia article on the Lord Mayor of London is very accurate.