Why is this Conversion important?

Ensco previously was included in the S&P 500 Index until December 2009 when it changed its corporate domicile to the U.K. and began trading in ADS form on the NYSE. Subsequently, Ensco was removed from the index due to eligibility rules that exclude companies listed in ADS form. By converting to a Share listing, Ensco’s eligibility for the S&P 500 Index will be restored, although there is no assurance that Ensco will be added to the S&P 500 Index in the future.

The majority of Ensco shareholders will be unaffected by the conversion from ADSs to Class A Ordinary Shares.

• Shareholders who hold their ADSs in a bank or brokerage account will not be required to take any action.
• Shareholders possessing physical certificates or who hold their ADSs in an account with the Company’s transfer agent (holders of record) will receive instructions by mail on how to convert their ADSs.