These excerpts taken from the BP 6-K filed May 22, 2008.
Forfeiture or surrender of shares for non-payment
37 If the requirements of any such notice as aforesaid are not complied with, any share in respect of which such notice has been given may at any time thereafter, before payment of all calls and interest and expenses due in respect thereof has been made, be forfeited by a resolution of the Directors to that effect. Such forfeiture shall include all dividends declared in respect of the forfeited share and not actually paid before forfeiture. The Directors may accept a surrender of any share liable to be forfeited hereunder.