Exhibit 99.6

8 October 2018

RE: Ensco plc and Rowan Companies plc to Combine

Dear [Valued Customer]:

Today, we announced that Ensco and Rowan have agreed to combine to create an industry-leading offshore driller built on core foundational values of safety, operational excellence, ethical behaviour and customer satisfaction. A copy of the press release is attached for your review.

This is an exciting development and one that we believe will enhance our ability to serve you and your needs. The combined company’s fleet will be among the most technologically advanced in the industry, with the ability to meet a broad range of deep- and shallow-water drilling requirements around the world. Customers will benefit from a wider range of sophisticated drilling solutions, a talented workforce and operations that span six continents.

The transaction combines Ensco’s and Rowan’s complementary fleets, geographic footprints, and capabilities. Within the combined company’s fleet of 28 floating rigs (drillships and semisubmersibles) will be 25 ultra-deepwater drilling rigs with an average age of six years — establishing this fleet as among the youngest and most capable in the industry. The combined company’s jackup rig fleet will be composed of 54 rigs, including 22 modern benign-water units and 16 high-specification harsh environment units.

Geographically, the combined company will be the most diverse offshore driller with current operations spanning six continents in nearly every major deep- and shallow-water basin around the world, including the Gulf of Mexico, Brazil, West Africa, North Sea, Mediterranean, Middle East, Southeast Asia and Australia.

Ensco and Rowan share a dedication to safety, operational excellence, employee development, customer satisfaction and technology and innovation, and you can continue to expect the highest levels of service from the combined company. The combined company will also be a financially stronger counterparty with greater liquidity and financial flexibility to continue investing in its fleet and innovation aimed at improving drilling efficiencies.

We expect to obtain the required regulatory, court and shareholder approvals in order to complete the combination during the first half of 2019. Upon closing, the company will operate under the leadership of Rowan President and Chief Executive Officer Tom Burke, who will serve as CEO of the combined company, and Ensco Chief Executive Officer and President Carl Trowell, who will serve as Executive Chairman. During the intervening period between this announcement and integration, both operations teams will continue to focus on our number one priority — safe and efficient operations.  After closing, we will begin to combine our two companies and we anticipate a smooth transition that will be seamless to our customers.

As always, we are grateful for your business and we appreciate the opportunity to provide you with the high-quality service you have come to expect from Ensco.

Sincerely,

[Marketing/Business Unit Customer Point of Contact]

Forward-Looking Statements

Statements included in this document regarding the proposed transaction, benefits, expected synergies and other expense savings and operational and administrative efficiencies, opportunities, timing, expense and effects of the transaction, financial performance, accretion to cash flows, revenue growth, credit ratings or other attributes of Ensco plc following the completion of the transaction and other statements that are not historical facts, are forward-looking statements (including within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended, and Section 27A of the Securities Act of 1933, as amended (the “Securities Act”)).  Forward-looking statements include words or phrases such as “anticipate,” “believe,” “contemplate,” “estimate,” “expect,” “intend,” “plan,” “project,” “could,” “may,” “might,” “should,” “will” and words and phrases of similar import.  These statements involve risks and uncertainties including, but not limited to, actions by regulatory authorities, rating agencies or other third parties, actions by the respective companies’ security holders, costs and difficulties related to integration of Ensco and Rowan, delays, costs and difficulties related to the transaction, market conditions, and Ensco’s financial results and performance following the completion of the transaction, satisfaction of closing conditions, ability to repay debt and timing thereof, availability and terms of any financing and other factors detailed in the risk factors section and elsewhere in Ensco’s and Rowan’s Annual Report on Form 10-K for the year ended December 31, 2017 and their respective other filings with the Securities and Exchange Commission (the “SEC”), which are available on the SEC’s website at www.sec.gov.  Should one or more of these risks or uncertainties materialize (or the other consequences of such a development worsen), or should underlying assumptions prove incorrect, actual outcomes may vary materially from those forecasted or expected.  All information in this document is as of today.  Except as required by law, both Ensco and Rowan disclaim any intention or obligation to update publicly or revise such statements, whether as a result of new information, future events or otherwise.

Important Additional Information Regarding the Transaction Will Be Filed With the SEC

In connection with the proposed transaction, Ensco and Rowan will file a joint proxy statement on Schedule 14A with the SEC.  To the extent Ensco effects the proposed transaction as a court-sanctioned scheme of arrangement between Rowan and Rowan’s shareholders under the UK Companies Act of 2006, as amended, the issuance of Ensco’s ordinary shares in the proposed transaction would not be expected to require registration under the Securities Act, pursuant to an exemption provided by Section 3(a)(10) under the Securities Act. In the event that Ensco determines to conduct an acquisition of Rowan pursuant to an offer or otherwise in a manner that is not exempt from the registration requirements of the Securities Act, it will file a registration statement with the SEC containing a prospectus with respect to Ensco’s ordinary shares that would be issued in the proposed transaction.  INVESTORS AND SECURITY HOLDERS OF ENSCO AND ROWAN ARE ADVISED TO CAREFULLY READ THE JOINT PROXY STATEMENT AND ANY REGISTRATION STATEMENT/PROSPECTUS (INCLUDING ALL AMENDMENTS AND SUPPLEMENTS THERETO) WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE TRANSACTION, THE PARTIES TO THE TRANSACTION AND THE RISKS ASSOCIATED WITH THE TRANSACTION.  A definitive joint proxy statement and any registration statement/prospectus, as applicable, will be sent to security holders of Ensco and Rowan in connection with the Ensco and Rowan shareholder meetings.  Investors and security holders may obtain a free copy of the joint proxy statement (when available), any registration statement/prospectus, and other relevant documents filed by Ensco and Rowan with the SEC from the SEC’s website at www.sec.gov.  Security holders and other interested parties will also be able to obtain, without charge, a copy of the joint proxy statement, any registration statement/prospectus, and other relevant documents (when available) by directing a request by mail or telephone to either Investor Relations, Ensco plc, 5847 San Felipe, Suite 3300, Houston, Texas 77057, telephone 713-789-1400, or Investor Relations, Rowan Companies plc, 2800 Post Oak Boulevard, Suite 5450, Houston, Texas 77056, telephone 713-621-7800.  Copies of the documents filed by Ensco with the SEC will be available free of charge on Ensco’s website at www.enscoplc.com under the tab “Investors.”  Copies of the documents filed by Rowan with the SEC will be available free of charge on Rowan’s website at www.rowan.com/investor-relations.

Participants in the Solicitation

Ensco and Rowan and their respective directors, executive officers and certain other members of management may be deemed to be participants in the solicitation of proxies from their respective security holders with respect to the transaction.  Information about these persons is set forth in Ensco’s proxy statement relating to its 2018 General Meeting of Shareholders and Rowan’s proxy statement relating to its 2018 General Meeting of Shareholders, as filed with the SEC on March 30, 2018 and April 3, 2018, respectively, and subsequent statements of changes in beneficial ownership on file with the SEC.  Security holders and investors may obtain additional information regarding the interests of such persons, which may be different than those of the respective companies’ security holders generally, by reading the joint proxy statement, any registration statement and other relevant documents regarding the transaction, which will be filed with the SEC.

No Offer or Solicitation

This document is not intended to and does not constitute an offer to sell or the solicitation of an offer to subscribe for or buy or an invitation to purchase or subscribe for any securities or the solicitation of any vote in any jurisdiction pursuant to the proposed transaction or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of

applicable law.  Subject to certain exceptions to be approved by the relevant regulators or certain facts to be ascertained, the public offer will not be made directly or indirectly, in or into any jurisdiction where to do so would constitute a violation of the laws of such jurisdiction, or by use of the mails or by any means or instrumentality (including without limitation, facsimile transmission, telephone and the internet) of interstate or foreign commerce, or any facility of a national securities exchange, of any such jurisdiction.

Service of Process

Ensco and Rowan are incorporated under the laws of England and Wales.  In addition, some of its officers and directors reside outside the United States, and some or all of its assets are or may be located in jurisdictions outside the United States.  Therefore, investors may have difficulty effecting service of process within the United States upon those persons or recovering against Ensco, Rowan or their respective officers or directors on judgments of United States courts, including judgments based upon the civil liability provisions of the United States federal securities laws. It may not be possible to sue Ensco, Rowan or their respective officers or directors in a non-U.S. court for violations of the U.S. securities laws.