Expiration of waiting period under Hart-Scott-R...

Serco and SI International announce expiration of waiting period under
Hart-Scott-Rodino Act

Serco Group plc (Serco) and SI International (NASDAQ: SINT) today announce that
the mandatory waiting period under the Hart-Scott-Rodino Antitrust Improvements
Act of 1976, in connection with the proposed acquisition of SI International by
Serco, has expired without the US Department of Justice or the Federal Trade
Commission requesting additional information relating to the proposed merger
agreement. This satisfies a condition to completion of the proposed
acquisition.

As announced on 27 August 2008, Serco has signed a definitive agreement to
acquire SI International and the transaction has been approved by the boards of
directors of both companies. The closing of the acquisition remains conditional
upon SI International stockholders' approval, other regulatory approvals
including Exon-Florio, and customary closing conditions. SI International's
stockholder vote to adopt the merger agreement and approve the merger is
scheduled for November 13, 2008. The proposed transaction is expected to be
completed before the end of 2008.

Ends

For further information please contact Serco Group plc: [phone]

Charles King, Head of Investor Relations

Dominic Cheetham, Corporate Communications Director

www.serco.com

About Serco

Serco is an international service company which combines commercial know-how
with a deep public service ethos.

We improve services by managing people, processes, technology and assets more
effectively. We advise policy makers, design innovative solutions, integrate
systems and - most of all - deliver to the public.

Serco supports governments, agencies and companies who seek a trusted partner
with a solid track record of providing assured service excellence. Our people
offer operational, management and consulting expertise in the aerospace,
defence, education, health, home affairs, local government, science,
technology, transport and the commercial sectors.

More information can be found at www.serco.com

About Serco North America

Serco North America is headquartered in Reston, Virginia and has 7,000
employees across the U.S., several Canadian provinces and other countries. It
designs and delivers human capital management, engineering, logistics, economic
cost analysis and integrated lifecycle transportation management solutions to
military, federal civil agencies, state and local government and commercial
customers. Its customers include the U.S. Army, Navy, Marine Corps, the FAA,
the Postal Service, the cities of San Francisco, Chicago and Hollywood, and
several commercial clients. More information can be found at www.serco-na.com.

About SI International

SI International, a member of the Russell 2000 and S&P SmallCap 600 indices, is
a provider of information technology and network solutions (IT) primarily to
the federal government. SI International combines technology and industry
expertise to provide a full spectrum of state-of-the-practice solutions and
services, from design and development to documentation and operations, to
assist clients in achieving their missions. SI International is ranked as the
42nd largest Federal Prime IT Contractor by Washington Technology and has
approximately 4,500 employees. More information about SI International can be
found at www.si-intl.com.

Additional information and where to find it:

This communication may be deemed to be solicitation material in respect of the
proposed acquisition of SI International by Serco. In connection with the
proposed acquisition, SI International has filed a definitive proxy statement
and other relevant documents in connection with the proposed transaction with
the United States Securities and Exchange Commission. A definitive proxy
statement has been mailed to security holders of SI International seeking
approval of the transaction. INVESTORS AND SECURITY HOLDERS ARE ADVISED TO READ
THE PROXY STATEMENT AND SUCH OTHER RELEVEANT MATERIALS, AS IT CONTAINS
IMPORTANT INFORMATION. Investors and security holders may obtain a free copy of
the proxy statement and any amendments or supplements filed by SI International
at the Securities and Exchange Commission's (SEC) web site at http://
www.sec.gov or at SI International's website at http://www.si-intl.com.
Investors also may obtain a free copy of the definitive proxy statement and
other documents filed with, or furnished to, the SEC from SI International by
directing a written request to SI International, Inc., 12012 Sunset Hills Road,
Suite 800, Reston, VA 20190, Attention: Company Secretary. SI International
stockholders will receive information at an appropriate time on how to obtain
transaction-related documents for free from SI International.

Disclaimer

Nothing in this press release should be construed as a profit forecast or be
interpreted to mean that the future earnings per share of Serco will
necessarily be the same as, or greater than, the earnings per share for
completed financial periods.

This document contains 'forward-looking statements' with respect to the
financial condition, results of operations and business of Serco and to certain
of Serco's plans and objectives with respect to these items.

Forward-looking statements are sometimes but not always identified by their use
of a date in the future or such words as 'anticipates', 'aims', 'due', 'could',
'may', 'should', 'expects', 'believes', 'intends', 'plans', 'targets', 'goal',
or 'estimates'. By their very nature, forward-looking statements are inherently
unpredictable, speculative and involve risk and uncertainty because they relate
to events and depend on circumstances that may or will occur in the future.

There are various factors that could cause actual results and developments to
differ materially from those expressed or implied by these forward-looking
statements. These factors include, but are not limited to, changes in the
economies, political situations and markets in which the Group operates;
changes in government priorities due to programme reviews or revisions to
strategic objectives: changes in the regulatory or competition frameworks in
which the Group operates; the impact of legal or other proceedings against or
which affect the Group; changes to or delays in programmes in which the Group
is involved; the completion of acquisitions and divestitures and changes in
exchange rates.

All written or verbal forward-looking statements, made in this document or made
subsequently, which are attributable to Serco or any other member of the Group
or persons acting on their behalf are expressly qualified in their entirety by
the factors referred to above. Serco does not intend to update these
forward-looking statements.

Safe Harbor Statement Under the Private Securities Litigation Reform Act of
1995

This news release may contain forward-looking statements for purposes of the
safe harbor provisions under The Private Securities Litigation Reform Act of
1995 that are based on management's beliefs, assumptions and current
expectations. Such statements are not considered historical facts and are
considered forward-looking statements under the federal securities laws. Actual
results may differ materially from those indicated by these forward-looking
statements as a result of various risks and uncertainties. Such risks include,
without limitation, the risk that the transaction will not be consummated as a
result of the failure to satisfy of any of the conditions precedent, such as
the ability of SI International to obtain the approval of SI International's
stockholders and to obtain government approvals required for closing the
transaction. As a result, there can be no assurance that the transaction will
be completed during the expected timeframe, or at all. SI International
undertakes no duty to update any forward-looking statements to conform the
statement to actual results or changes in expectations that may arise after the
date of this release. We caution you not to place undue reliance upon any such
forward-looking statements.

SI International and its directors, executive officers and other members of its
management and employees may be deemed to be participants in the solicitation
of proxies from its stockholders in connection with the proposed merger.
Information about the directors and executive officers of SI International and
their respective interests in SI International by security holdings or
otherwise is set forth in its proxy statement relating to the 2008 annual
meeting of stockholders, which was filed with the SEC on 18 April 2008.
Investors may obtain additional information regarding the interest of the
participants by reading the proxy statement regarding the acquisition.