RIGHTS ISSUE

Access to this section of the website may be restricted under securities laws in certain countries (each an "Excluded Territory"). You are required to confirm certain matters (including that you are not resident in nor do you act on behalf of someone who is in an Excluded Territory) before you may obtain access to the information on this section of the website. These materials are not directed at or accessible by persons located in the United States, Canada, France, Japan, Malaysia, New Zealand, South Africa or Switzerland or in any other jurisdiction where it would be unlawful to do so.

IMPORTANT INFORMATION

Proposed 3 for 4 Rights Issue of new shares at an issue price of 24 pence per share (the "Rights Issue").

This area of the website (the "Site") contains documents and information relating to the Rights Issue. The information contained in this Site is made available in good faith and for information purposes only and is subject to the terms and conditions set out below.

The full terms and conditions of the Rights Issue are set out in the Prospectus and the Provisional Allotment Letter (where applicable). The Rights Issue cannot be validly accepted by holders of Costain shares or any other person through means of downloading a copy of any document from this website. For all enquiries relating to the Rights Issue please contact Lloyds TSB Registrars on 0870 606 3021 or +44 121 415 0265.

Access to the Site

If you would like to view the Site, please read this notice carefully. This notice applies to all persons who view the Site and, depending on where you are located, may affect your rights or responsibilities. Costain reserves the right to amend or update this notice at any time and you should, therefore, read it in full each time you visit the Site. In addition, the contents of the Site may be amended at any time in whole or in part at the sole discretion of Costain.

Overseas persons

As a consequence of legal restrictions, the release, publication or distribution of information contained on the Site in certain jurisdictions or to certain persons may be restricted or unlawful. All persons resident outside the United Kingdom who wish to view the Site must first satisfy themselves that they are not subject to any local requirements that prohibit or restrict them from doing so and should inform themselves of, and observe, any applicable legal or regulatory requirements applicable in their jurisdiction. In particular, if you are (or you act on behalf of someone who is a) resident in a country that renders the accessing of the Site or parts thereof illegal, whether or not subject to making certain notifications or taking other action, you should not view the Site.

In particular, unless otherwise determined by Costain and permitted by applicable law and regulation, it is not intended that these materials be accessible by persons located in the United States or by persons located in Canada, France, Japan, Malaysia, New Zealand, South Africa or Switzerland or in any other jurisdiction where it would be unlawful to do so.

It is your responsibility to satisfy yourself as to the full observance of any relevant laws and regulatory requirements. If you are in any doubt, you should not continue to seek to access the Site.

You should not forward, transmit or show the information or documents contained in the Site to any person. In particular, you should not forward or transmit the information or documents contained therein to any jurisdiction where it would be unlawful to do so.

The information contained in these materials does not constitute or form part of any offer or invitation to sell or issue, or any solicitation of any offer to acquire, New Ordinary Shares, Provisional Allotment Letters, Nil Paid Rights, Fully Paid Rights and/or to take up any entitlements to Nil Paid Rights in any jurisdiction in which such an offer or solicitation is unlawful. The New Ordinary Shares, the Nil Paid Rights, the Fully Paid Rights and the Provisional Allotment Letters have not been and will not be registered under the Securities Act or under any relevant securities laws of any state or other jurisdiction of the United States and may not be offered, sold, pledged, taken up, exercised, resold, renounced, transferred or delivered, directly or indirectly, within the United States or to, or for the account of, US persons absent registration or an applicable exemption from the registration requirements of the Securities Act and in compliance with state securities laws. The New Ordinary Shares, the Nil Paid Rights, the Fully Paid Rights and the Provisional Allotment Letters have not been approved or disapproved by the SEC, any state securities commission in the United States or any other US regulatory authority, nor have any of the foregoing authorities passed upon or endorsed the merits of the offering of the New Ordinary Shares, the Nil Paid Rights, the Fully Paid Rights or the Provisional Allotment Letters or the accuracy or adequacy of the information contained in this Site. Any representation to the contrary is a criminal offence in the United States. In addition, none of the New Ordinary Shares, the Nil Paid Rights, the Fully Paid Rights or the Provisional Allotment Letters will qualify for distribution under any of the relevant securities laws of Canada, France, Japan, Malaysia, New Zealand, South Africa or Switzerland. Accordingly, the New Ordinary Shares, the Nil Paid Rights, the Fully Paid Rights and the Provisional Allotment Letters may not be offered, sold, pledged, taken up, exercised, resold, renounced, transferred or delivered, directly or indirectly, within Canada, France, Japan, Malaysia, New Zealand, South Africa or Switzerland.

Responsibility

The documents included in the Site speak only at the specified date of the relevant document and Costain has, and accepts, no responsibility or duty to update such documents.

If you are in any doubt about the contents of the Site or the action you should take, you should seek your own financial advice from an independent financial adviser authorised under the Financial Services and Markets Act 2000 or, if you are located outside the United Kingdom, from an appropriately authorised independent financial adviser.

THE DOCUMENTS MAY NOT BE VIEWED, DOWNLOADED BY ANY PERSON OR FORWARDED TO ANY PERSON IN THE UNITED STATES, CANADA, FRANCE, JAPAN, MALAYSIA, NEW ZEALAND, SOUTH AFRICA OR SWITZERLAND.

Confirmation of understanding and acceptance

Electronic versions of these materials are not directed at or accessible by persons located in the US, Canada, France, Japan, Malaysia, New Zealand, South Africa or Switzerland or in any other jurisdiction where it would be unlawful to do so.

Therefore, in order to view these materials you must make the following confirmation:

(i)I certify that I am not (nor do I act on behalf of someone who is a) resident in the
Canada, France, Japan, Malaysia, New Zealand, South Africa or Switzerland or
any other country that renders the accessing of the Site or parts thereof illegal;

(ii)Costain is lawfully entitled to make the content of the Site available to me under
all applicable laws;

(iii)I certify that I will not print, download, or otherwise seek to copy, forward, transfer
or distribute these materials to any other person at any time;

(iv)I represent and warrant to Costain that I intend to access the Site for information
purposes only; and

(v)I have read and understood the disclaimer set out above. I understand that it may
affect my rights. I agree to be bound by its terms. I confirm that I am permitted
to view the electronic versions of these materials.

If you are not able to give this confirmation, you should click on CANNOT CONFIRM below.

I confirm | I cannot confirm

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