This excerpt taken from the BP 20-F filed Jun 30, 2005.
Specific Provisions relating to Options
5.1 The Committee may, at its absolute discretion, grant Options during any Grant Period. The Option Exercise Price of such Options shall be determined by the Committee at its absolute discretion, but shall not be less than the Market Value of a Share on the Dealing Day preceding the Date of Grant or the average of the Market Values of a Share on the three Dealing Days prior to the Date of Grant.
5.2 All Options will be subject to a demanding performance condition.
5.3 The Committee will not grant Options unless it considers that an Option grant is supported by the underlying performance of the Company's business.
5.4 The Grant Letter issued under rule 2.4 shall specify, inter alia, the following:
5.5 Any Grant Letter issued pursuant to rule 5.4 shall ensure that legally enforceable rights are created in favour of the Participant.