According to some reports -see here:
http://groups.google.co.uk/group/alt.talk.royalty/browse_thread/thread/b2904ff2085fa35f/7deb70a783c92e03?hl=en#7deb70a783c92e03
Boris Johnson, standing to day in the election for the office of Mayor
of London, is a descendant of Frederick Lewis, Prince of Wales, and a
cousin, albeit several times removed, of Queen Elizabeth II and of the
Conservative party leader David Cameron.
viz:-
Frederick Prince of Wales = Augusta of Coburg
(1707-51)
\
Augusta of Gt Britain =Karl II Duke of Brunswick 1735-1806
(1737-1813)
\
Auguste of Brunswick =Friedrich Prince later King of Württemberg
(1764-88)
\
Paul Prince of Württemberg
1785-1852, had illegitimate daughter by
Friederike Margarethe Porth
\
Karoline Adelheid Pauline von Rottenberg =Kark Freiherr von
Pfeffel
\
Hubert Freiherr von Pfeffel
b 1843
\
Marie Luise Freiin von Pfeffel =Stanley Williams
b 1882
\
Irene Williams m. Osman Wilfred Kemal, later Johnson
\
Stanley Patrick Johnson b 1940 m. Charlotte Fawcett
\
Alexander Boris Pfeffel Johnson =(1) Allegra Mostyn-Owen
and (2) Marina Wheeler.