These excerpts taken from the BP 6-K filed May 22, 2008.
Voting in person or by proxy
80 On a poll votes may be given either personally or by proxy and a person entitled to more than one vote:
(i) may vote in respect of some of his shares in person and in respect of others of them by proxy; and
(ii) need not use all his votes or cast all the votes he uses (either in person or by proxy) in the same way.