I'm in England but not London. Anyway, the Tower of London is
well worth a visit imo. The "Beefeaters" (tour guides) are all ex
soldiers who have served at least about 22 years. Great humour and
insight.
Or, you could do a search for Litivinenko on google. He is the
ex-russian FSB agent who was recently poisoned with some radiation
material in a Sushi Bar in London. Its all very 'spy thriller' like
and highlights how international and important London is.