[C.E. Unterberg, Towbin Letterhead]

                                                                       Exhibit 4

                                                                 April 14, 2003

Special Committee of the Board of Directors
Professional Staff plc
Buckland House
Waterside Drive
Langley Business Park
Slough, SL3 6EZ
United Kingdom

Attention: Jerry Benjamin, John Maynard

Gentlemen:

We understand that Professional Staff plc ("Professional Staff") is considering
a proposal (the "Proposal") by Ohsea Limited ("Ohsea") for the acquisition by
Ohsea, by means of a scheme of arrangement under section 425 of the Companies
Act 1985, of all the issued share capital, nominal value 2 pence per share, of
Professional Staff (the "Capital Stock"), other than (i) shares of Capital Stock
owned or controlled by Ohsea, CS Services Limited ("CS Services") and the
beneficial owners of Ohsea and CS Services (the "Beneficial Owners") and (ii)
certain shares of Capital Stock owned or controlled by Benjamin P. Blackden,
Andrew R. Dixey and the trusts and family members of Mr. Blackden and Mr. Dixey
(collectively with Ohsea, CS Services and the Beneficial Owners, the "Ohsea
Parties"). Pursuant to the Proposal, (a) each holder of American Depositary
Shares of Professional Staff (the "ADSs"), other than the Ohsea Parties, would
receive, in cash, $2.07 per ADS (the "ADS Consideration") and (b) each holder of
Capital Stock, other than the Ohsea Parties and the holders of the ADSs, would
receive, in cash, $2.10 per share of such Capital Stock (the "Ordinary Share
Consideration"). You have informed us that the $0.03 per share differential
between the Ordinary Share Consideration and the ADS Consideration results from
The Bank of New York, as depositary for the ADSs, retaining $0.03 per ADS for
fees and expenses in accordance with the Deposit Agreement among Professional
Staff, The Bank of New York and the owners and beneficial owners of the ADSs
(the "Deposit Agreement"). The terms and conditions of the Proposal are set
forth more fully in the Scheme Document (the "Scheme Document").

The board of directors of Professional Staff has appointed a committee of
independent directors of Professional Staff (the "Special Committee") to
consider the Proposal. In connection with the Special Committee's consideration
of the Proposal, the Special Committee has asked for our opinion as to whether
the ADS Consideration is fair, from a financial point of view, to the holders of
the ADSs (other than the Ohsea Parties).

For purposes of this opinion, we have reviewed the Proposal, a draft of the
Scheme Document and certain related documents; reviewed certain publicly
available financial statements and other information of Professional Staff; and
analyzed certain internal



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April 14, 2003

financial statements and other financial and operating data and financial
forecasts of Professional Staff prepared by Professional Staff's management (the
"Company Forecasts"). We have also held discussions with members of the senior
management of Professional Staff regarding the financial information referred to
above and the past and current business operations, financial condition and
future prospects of Professional Staff. In addition, we have reviewed the
reported price and trading activity of the Capital Stock; compared certain
financial information of Professional Staff, including market prices and
valuation multiples, for Professional Staff with similar information for certain
other comparable publicly traded companies we deemed relevant; analyzed, using
publicly available information, the consideration offered, and the implied
transaction value multiples paid or proposed to be paid, in acquisition
transactions that were announced since January 1, 1999 in the staffing services
industry that we deemed relevant and compared the terms of these acquisition
transactions to the terms of the Proposal; and performed such other studies and
analyses as we considered appropriate.

For purposes of rendering this opinion, we have assumed and relied upon, without
assuming any responsibility for independent verification, the accuracy and
completeness of all of the financial and other information publicly available or
provided to us by Professional Staff and its management and agents. In addition,
in rendering this opinion, we have assumed, with your consent and without
assuming any responsibility for independent verification, that the Company
Forecasts (and the assumptions and bases therefor) have been reasonably prepared
by Professional Staff in good faith and on a basis reflecting the best currently
available estimates, assumptions and judgments of the management of Professional
Staff as to the future financial condition and performance of Professional
Staff.

In providing this letter, we have assumed, with your consent and without
assuming any responsibility for independent verification, that (i) The Bank of
New York, as depositary for the ADSs, will not retain in excess of $0.03 per ADS
for fees and expenses in accordance with the Deposit Agreement or otherwise,
(ii) the definitive Scheme Document will not differ in any material respect from
the draft Scheme Document reviewed by us, (iii) the representations and
warranties of the parties in the Scheme Document are, and will be, true and
correct as of the date hereof and as of the closing date of the Proposal and
(iv) the Proposal will have the tax and legal effects contemplated in the Scheme
Document. We have also assumed, with your consent and without assuming any
responsibility for independent verification, that the historical financial
statements of Professional Staff reviewed by us have been prepared and fairly
presented in accordance with generally accepted accounting principles in the
United States, consistently applied. In addition, we have assumed that all
conditions to the consummation of the Proposal will be fulfilled and that the
Proposal will be consummated in a timely manner.

We have not made an independent evaluation or appraisal of the assets and
liabilities of Professional Staff or any of its subsidiaries and we have not
been furnished with any such evaluation or appraisal. Our advisory services and
the opinion expressed herein are



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provided for the information and assistance of the Special Committee in
connection with its consideration of the Proposal, and our opinion is limited to
the fairness of the ADS Consideration, from a financial point of view, to the
holders of the ADSs (other than the Ohsea Parties). Our opinion does not address
the relative merits of the Proposal as compared to any alternative business
strategy that might be available to Professional Staff nor does our opinion
address Professional Staff's underlying business decision to effect the Proposal
or constitute a recommendation of the Proposal to the Special Committee or
Professional Staff's shareholders. This letter is not intended as a substitute
for the exercise of the business judgment of the Special Committee in reviewing
the Proposal. Finally, our opinion does not constitute an opinion or imply a
conclusion as to the current price per share of the Capital Stock or the price
at which Capital Stock will trade at any future time.

Our opinion is based upon market, economic and other conditions as they exist
and can be evaluated on the date hereof, and we assume no responsibility to
update or revise our opinion based upon circumstances or events occurring after
that date. It should be understood that subsequent developments may affect the
conclusions expressed in this opinion.

Based upon and subject to the foregoing and based upon such other matters as we
considered relevant, it is our opinion that, as of the date hereof, the ADS
Consideration is fair, from a financial point of view, to the holders of the
ADSs (other than the Ohsea Parties).

We are acting as the Special Committee's financial advisor in connection with
the Proposal and will receive a fee for the rendering of this opinion. In
addition, Professional Staff has agreed to indemnify us for certain liabilities
and reimburse us for certain of our expenses that may arise out of our
engagement. In the ordinary course of our business, we may actively trade in the
securities of Professional Staff for our own account and for the accounts of our
customers and, accordingly, may at any time hold long or short positions in such
securities. Thomas I. Unterberg, the Chairman of C.E. Unterberg, Towbin, is a
director of Professional Staff and directly owns 40,000 shares of Capital Stock
and holds 21,800 shares of Capital Stock through his 401K plan. In addition, Mr.
Unterberg's wife owns 750 shares of Capital Stock. As of April 11, 2003, C.E.
Unterberg, Towbin held (i) 600,000 shares of Capital Stock in investment
accounts owned by C.E. Unterberg, Towbin, (ii) 100,000 shares of Capital Stock
held by C.E. Unterberg, Towbin Capital Partners I, L.P., (iii) 371,455 shares of
Capital Stock in market making accounts, (iv) 50,000 shares of Capital Stock in
the account of a charitable foundation for which Mr. Unterberg acts as trustee
and (v) 50 shares of Capital Stock held in accounts of employees of C.E.
Unterberg, Towbin. C.E. Unterberg, Towbin has provided investment banking
services and advice to Professional Staff in the past for which it has received
compensation standard with industry practice.

The foregoing opinion letter is provided for the information and assistance of
the Special Committee in connection with its consideration of the Proposal and
is not intended to be



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and does not constitute a recommendation to any shareholder of Professional
Staff as to how such shareholder should vote, or take any other action, with
respect to the Proposal. This opinion is not intended to confer any rights or
remedies upon any employee, creditor, shareholder or other equity holder of
Professional Staff or any other party. Our opinion is not to be disclosed to or
relied upon by any other person (including any shareholder of Professional
Staff) or used, circulated, quoted or otherwise referred to for any other
purpose, nor is it to be filed with, included in or referred to in whole or in
part in any publicly available statement or document, except in accordance with
our prior written consent.

                                                     Very truly yours,

                                                     C.E. Unterberg, Towbin