Annual Information Update

Costain Group PLC("Costain" or the "Company")

Annual Information Update for the 12 months up to and including 30 March 2012

1. RIS Announcements

The following UK regulatory announcements have been made via a Regulatory Information Service. A copy of these announcements can be obtained from the London Stock Exchange website, www.londonstockexchange.com/marketnews

Date Headline

2011

04.04.2011 Mouchel 'no offer' announcement

07.04.2011 Acquisition of ClerkMaxwell Limited

08.04.2011 TR-1 Notification : Henderson Global Investors Limited

08.04.2011 Employee Share Plans

11.04.2011 Disposal of Interests in Zimbabwe

13.04.2011 Total Voting Rights and Share Capital

13.04.2011 Long-term Incentive Plan

14.04.2011 Deferred Share Bonus Plan

26.04.2011 Scrip Dividend Reference Price

27.04.2011 Exercise of Call Option re ClerkMaxwell Limited

28.04.2011 Annual Information Update

03.05.2011 TR-1 Notification Henderson Global Investors Limited

05.05.2011 Interim Management Statement

05.05.2011 Results of AGM

19.05.2011 Final Dividend 2010 and Scrip Issue

25.05.2011 Water Contract Extensions

31.05.2011 Change of Advisor - Appointment of N M Rothschild

13.06.2011 A465 Heads of Valleys Contract South Wales

17.06.2011 Block Listing Application 

30.06.2011 Pre-close Trading Update

30.06.2011 Reading Station Contract

01.07.2011 Total Voting Rights and Share Capital - SAYE

26.07.2011 Paddington Crossrail Contract

29.07.2011 Total Voting Rights and Share Capital - SAYE

22.08.2011 Acquisition of Promanex

25.08.2011 Interim Results for the half-year ended 30 June 2011

02.09.2011 Total Voting Rights and Share Capital - SAYE

04.10.2011 Total Voting Rights and Share Capital - SAYE

13.10.2011 SAYE New Scheme Options

13.10.2011 Share Purchase by Director

27.10.2011 Interim Dividend 2011 - Scrip Alternative

31.10.2011 Total Voting Rights and Share Capital

01.11.2011 London Bridge Contract

07.11.2011 Interim Management Statement

30.11.2011 Total Voting Rights and Share Capital

20.12.2011 Transactions in Shares re PDMRs

2012

01.01.2012 Total Voting Rights and Share Capital

05.01.2012 Pre-close Trading Update

23.02.2012 Costain Pension Scheme

02.03.2012 Total Voting Rights and Share Capital

07.03.2012 Full year results for the year ending 31 December 2011

08.03.2012 OPA contract

30.03.2012 Notice of AGM and Annual Report for the year ended 31 December 2011

2. Documents filed at Companies House

The Company has also made the following filings with Companies House. Copies of these documents can be obtained from Companies house, Crown Way, Cardiff, CF14 3UZ (by e-mail at [email protected] or, if you are a registered user, through Companies House Direct at www.direct.companieshouse.gov.uk ).

Date Description

2011

04.04.11 AA - Group of Companies Accounts made up to 31.12.10

15.04.11 SH01 - 05.04.11 Statement of Capital

14.06.11 TM02 - Appointment Terminated Secretary Clive Franks 31.05.11

14.06.11 AP03 - Secretary Appointed Tracey Alison Wood 01.06.11

14.06.11 Resolution : Company Business 05.05.2011

22.08.11 SH01 - 05.08.11 Statement of Capital

22.08.11 SH01 - 29.07.11 Statement of Capital

22.08.11 SH01 - 22.07.11 Statement of Capital

22.08.11 SH01 - 15.07.11 Statement of Capital

22.08.11 SH01 - 08.07.11 Statement of Capital

22.08.11 SH01 - 01.07.11 Statement of Capital

23.08.11 SH01 - 12.08.11 Statement of Capital

31.08.11 SH01 - 26.08.11 Statement of Capital

07.09.11 SH01 - 02.09.11 Statement of Capital

27.09.11 SH01 - 09.09.11 Statement of Capital

27.09.11 SH01 - 16.09.11 Statement of Capital

13.10.11 SH01 - 23.09.11 Statement of Capital

13.10.11 SH01 - 30.09.11 Statement of Capital

19.10.11 SH01 - 07.10.11 Statement of Capital

19.10.11 SH01 - 14.10.11 Statement of Capital

08.11.11 SH01 - 28.10.11 Statement of Capital

24,11,11 SH01 - 04.11.11 Statement of Capital

24.11.11 SH01 - 11.11.11 Statement of Capital

24.11.11 SH01 - 18.11.11 Statement of Capital

08.12.11 CC04 - Statement of Company's Objects

08.12.11 AD02 - Sail Address

19.12.11 SH01 - 09.12.11 Statement of Capital

2012

03.01.12 SH01 - 16.12.11 Statement of Capital

09.01.12 SH01 - 23.12.11 Statement of Capital

09.01.12 SH01 - 30.12.11 Statement of Capital

10.01.12 SH01 - 05.01.12 Statement of Capital

3. Documents published and sent to shareholders

01.04.2011 Annual Report and Accounts 2010, Notice of AGM, Proxy Card

06.09.2011 Interim Report and Accounts 2011

30.03.2012 Annual Report and Accounts 2011, Notice of AGM, Proxy Card

Copies of information released can be obtained from the Company's Registered Office at:

Costain House

Vanwall Business Park

Maidenhead

Berkshire

SL6 4UB

27 April 2012

Enquiries: