This excerpt taken from the DEO 20-F filed Sep 15, 2008.
In any case where the Company is obliged to account:
(i) for any tax (or similar liabilities) in any jurisdiction for which the Optionee in question is liable by virtue of the exercise of an Option; or
(ii) for any social security or other contributions recoverable from the Optionee in question;
(together, the Tax Liability) the Company may recover the tax from the Optionee in question in such manner as the Board or the Committee shall think fit and (without prejudice to the generality of the foregoing) no ADSs shall be issued or transferred to that Optionee unless he has either:
(i) made a payment to the Company of an amount equal to the Tax Liability; or
(ii) entered into arrangements with the Company to secure that such a payment is made (whether by authorising the Company to procure the sale of some or all of the ADSs on his behalf and authorising the payment to the Company of the relevant amount of the proceeds of sale or otherwise).