Exhibit 24.2
                               POWER OF ATTORNEY
       For Executing Forms 3, 4 and 5, Form 144 and Schedules 13D and 13G

       Known by all these present, that the undersigned hereby constitutes and
appoints each of Rimma Khafizova and Brett Riesenfeld, or either of them signing
singly, and with full power of substitution, the undersigned's true and lawful
attorney-in-fact to:

(1)    execute for and on behalf of the undersigned (a) Forms 3, 4 and 5
       (including amendments thereto) in accordance with Section 16(a) of the
       Securities Exchange Act of 1934 and the rules thereunder, (b) Form 144
       and (c) Schedules 13D and 13G (including amendments thereto) in
       accordance with Sections 13(d) and 13(g) of the Securities Exchange Act
       of 1934 and the rules thereunder, but only to the extent each such form
       or schedule relates to the undersigned's beneficial ownership of
       securities of Magellan Petroleum Corporation;

(2)    do and perform any and all acts for and on behalf of the undersigned that
       may be necessary or desirable to complete and execute any such Form 3, 4
       or 5, Form 144 or Schedule 13D or 13G (including amendments thereto) and
       timely file such Forms or Schedules with the Securities and Exchange
       Commission and any stock exchange, self-regulatory association or any
       other authority, and provide a copy as required by law or advisable to
       such persons as the attorney-in-fact deems appropriate; and

(3)    take any other action of any type whatsoever in connection with the
       foregoing that, in the opinion of each such attorney-in-fact, may be of
       benefit to, in the best interest of, or legally required of the
       undersigned, it being understood that the documents executed by the
       attorney-in-fact on behalf of the undersigned pursuant to this Power of
       Attorney shall be in such form and shall contain such terms and
       conditions as the attorney-in-fact may approve in the attorney-in-fact's
       discretion.

       The undersigned hereby grants to each attorney-in-fact full power and
authority to do and perform all and every act and thing whatsoever requisite,
necessary or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that the attorney-in-fact, or the
attorney-in-facts substitutes or substitute, shall lawfully do or cause to be
done by virtue of this Power of Attorney and the rights and powers herein
granted. The undersigned acknowledges that the foregoing attorneys-in-fact, and
their substitutes, in serving in such capacity at the request of the
undersigned, are not assuming any of the undersigned's responsibilities to
comply with Section 16 of the Securities Exchange Act of 1934.

       The undersigned agrees that each such attorney-in-fact may rely entirely
on information furnished orally or in writing by or at the direction of the
undersigned to the attorney-in-fact. The undersigned also agrees to indemnify
and hold harmless each such attorney-in-fact against any losses, claims, damages
or liabilities (or actions in these respects) that arise out of or are based
upon any untrue statements or omissions of necessary facts in the information
provided by or at the direction of the undersigned, or upon the lack of
timeliness in the delivery of information by or at the direction of the
undersigned, to such attorney-in-fact for purposes of executing, acknowledging,
delivering or filing Forms 3, 4 or 5, Form 144 or Schedule 13D or 13G (including
amendments thereto) and agrees to reimburse such attorney-in-fact on demand for
any legal or other expenses reasonably incurred in connection with investigating
or defending against any such loss, claim, damage, liability or action.

       This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4 and 5, Form 144 and
Schedules 13D and 13G (including amendments thereto) with respect to the
undersigned's holdings of and transactions in securities issued by Magellan
Petroleum Corporation, unless earlier revoked by the undersigned in a signed
writing delivered to the foregoing attorneys-in-fact. This Power of Attorney
revokes all other powers of attorney that the undersigned has previously granted
concerning the matters described herein.

       IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of the date written below.

                                        One Stone Energy Partners GP, L.L.C.

                                        By:    /s/ Robert Israel
                                               ---------------------------------
                                        Name:  Robert Israel
                                        Title: Managing Member

                                        May 15, 2013