Exhibit 5.1

Dear Sirs,

Ensco plc (the “Company”)
Proposed offering of new ordinary shares

We have acted solely as English counsel to the Company, a public limited company incorporated in England and Wales, in connection with the issue of up to 65,550,000 Class A ordinary shares of US$0.10 each in the capital of the Company (the “Securities”) as authorised by the unanimous written resolutions of the board of directors of the Company dated 8 April 2016 approving such offering in principle (the “Board Resolutions”).

In rendering the opinion set forth below, we have examined and relied upon originals or copies, certified or otherwise identified to our satisfaction, of: (i) the Underwriting Agreement dated 14 April 2016 between the Company, Goldman, Sachs & Co. (“GS”) and Morgan Stanley & Co. LLC (“MS”); (ii) the Subscription and Transfer Agreement dated 14 April 2016 between the Company, ESV Jersey Limited (“JerseyCo”) and MS; (iii) the Put and Call Option Agreement dated 14 April 2016 between the Company, JerseyCo and MS; (iv) copies of the minutes of a meeting of a committee of the board of directors of the Company on 14 April 2016 (the “Pricing Committee Minutes”); (v) the Board Resolutions; and (vi) copies (as of 20 April 2016), of the memorandum and articles of association (and any resolutions or agreements amending the same) of the Company and the certificates of incorporation of the Company.  Terms and expressions defined in the Underwriting Agreement have the same meanings when used in this letter.

We have assumed, without independent investigation, the genuineness of all signatures and the conformity to original documents of all documents submitted to us as certified, photostatic, reproduced, or conformed copies.  In addition, we have assumed that: (i) the annual general meeting of the Company held on 18 May 2015 was duly convened and held and the resolution numbered 2 (Authority to allot shares) set out in the notice of such meeting was duly passed and filed in accordance with the Companies Act 2006 (as amended), remains in full force and effect and US$3,413 of aggregate nominal value of Class A ordinary shares have been issued pursuant to such authority as at the date of this opinion; (ii) the directors of the Company have acted in accordance with their duties as directors and for a proper purpose under all applicable laws and the memorandum and articles of association of the Company in so far as is relevant to this opinion

letter; and (iii) there has been and will have been no contravention of any of the provisions of the Financial Services and Markets Act 2000 (“FSMA”) or any applicable secondary legislation made under it by anyone in relation to the offering of the Securities (including without limitation, the provisions of sections 19 and 21 of FSMA).  As to certain other matters of fact, both express and implied, we have relied upon representations, statements and certificates of officers of the Company.

Based upon the above, and subject to the stated assumptions, we are of the opinion that, when issued in accordance with the Board Resolutions and the Pricing Committee Minutes and subject to the statutory notification to the Registrar of Companies of the allotment of the Securities (as required by the Companies Act 2006 (as amended)), the Securities will be duly authorised, validly issued, fully paid and non-assessable.

Our opinion set forth herein is limited to English law and to the extent that judicial and regulatory orders or consents, approvals, licences, authorisations, filings or registrations for governmental or other public authorities are relevant, to those required under such law.  We express no opinion and make no representation with respect to any other laws or the law of any other jurisdiction.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to any references to this firm in the prospectus contained therein.  In giving this consent, we do not admit that we are experts within the meaning of section 11 of the Securities Act 1933 or within the category of persons whose consent is required under section 7 of the Securities Act 1933.

Our opinion is expressly limited to the matters set forth above and we render no opinion, whether by implication or otherwise, as to any other matters relating to the Company or any other document or agreement involvement with the issuance of the Securities.  We assume no obligation to advise you of facts, circumstances, events or developments which may hereafter be brought to our attention and which may alter, affect, or modify the opinions expressed herein.

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