These excerpts taken from the BP 6-K filed May 22, 2008.
Vacation of office by a Director
99 The office of a Director shall be vacated in any of the following events, namely:
(i) if he shall become prohibited by law from acting as a Director;
(ii) if he shall resign in writing left at the Office or if he shall in writing offer to resign and the Directors shall resolve to accept such offer;
(iii) if he shall have a receiving order made against him or shall compound with his creditors generally;
(iv) if in England or elsewhere an order shall be made by any court claiming jurisdiction in that behalf on the ground (however formulated) of mental disorder for his detention or for the appointment of a guardian or for the appointment of a receiver or other person (by whatever name called) to exercise powers with respect to his property or affairs.