Exhibit 12.1

SECTION 302 CERTIFICATION

CEO
Certification

I, Andrew Mackenzie, certify that:



|1. | I have reviewed this annual report on Form 20-F of BHP Billiton Plc and BHP Billiton Limited;
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|2. | Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such
statements were made, not misleading with respect to the period covered by this report;
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|3. | Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the
companies as of, and for, the periods presented in this report;
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|4. | The companies other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over
financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d15(f)) for the companies and have:
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| | a) | Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the companies, including their
consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;
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| | b) | Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of
financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;
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| | c) | Evaluated the effectiveness of the companies disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the
period covered by this report based on such evaluation; and
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| | d) | Disclosed in this report any change in the companies internal control over financial reporting that occurred during the period covered by the annual report that has materially affected, or is reasonably likely to
materially affect, the companies internal control over financial reporting; and
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|5. | The companies other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the companies auditors and the audit committee of the
companies board of directors (or persons performing the equivalent functions):
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| | a) | All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the companies ability to record,
process, summarise and report financial information; and
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| | b) | Any fraud, whether or not material, that involves management or other employees who have a significant role in the companies internal control over financial reporting.
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|                     |  |                        
|-------------------- |  | -----------------------
|                    
|/s/ Andrew Mackenzie
|Name:                |  | Andrew Mackenzie       
|Title:               |  | Chief Executive Officer
|Date:                |  | 23 September 2015