Greenhill
& Co., Inc.
300
Park Avenue
New
York, NY 10022
April 28, 2009
GHL
Acquisition Corp.
300 Park
Avenue
New York,
NY 10022
Iridium
Holdings LLC
6707
Democracy Boulevard, Suite 300
Bethesda,
MD 20817
Ladies
and Gentlemen:
Reference is made to (i) the letter
agreement, dated September 22, 2008, among Greenhill & Co., Inc., GHL
Acquisition Corp. (the “Company”) and Iridium Holdings LLC (the “First Letter
Agreement”) and (ii) the Transaction Agreement, dated September 22, 2008, among
the Company, Iridium Holdings LLC and the sellers listed on the signature pages
thereto, as amended on the date hereof (the “Transaction
Agreement”).
In addition to the forfeitures pursuant
to the First Letter Agreement, subject to and simultaneously with the closing
under the Transaction Agreement, Greenhill & Co., Inc. will forfeit an
additional 2,000,000 warrants of the Company originally purchased in a
private placement consummated on February 21, 2008.
In the event that the
Transaction Agreement is terminated in accordance with its terms, this letter
agreement shall terminate immediately and have no further force or
effect.
This letter agreement shall be governed
by and construed in accordance with the law of the State of Delaware, without
regard to the conflicts of law rules of such state. This letter
agreement may be signed in any number of counterparts, each of which shall be an
original, with the same effect as if the signatures thereto and hereto were upon
the same instrument.
[Signature page
follows]
If the above correctly
reflects our understanding and agreement with respect to the foregoing matters,
please so confirm by signing and returning the enclosed copy of this letter
agreement.