Holding(s) in Company

NOTIFICATION OF MAJOR HOLDINGS (to be sent to the relevant issuer and to the FCA in Microsoft Word format if possible)i

1a. Identity of the issuer or the underlying issuer of existing shares to which voting rights are attachedii:

Costain Group

GB00B64NSP76

1b. Please indicate if the issuer is a non-UK issuer (please mark with an "X" if appropriate)

2. Reason for the notification (please mark the appropriate box or boxes with an "X")

An acquisition or disposal of voting rights

x

An acquisition or disposal of financial instruments

An event changing the breakdown of voting rights

Other (please specify)iii:

3. Details of person subject to the notification obligationiv

Name

KBI Global Investors Ltd.

As controller of the voting rights directly or indirectly via a subsidiary

City and country of registered office (if applicable)

Dublin, Ireland

4. Full name of shareholder(s) (if different from 3.)v

Name

KBI Global Investors Ltd

KBI Global Investors (North America) Ltd

KBI Aquarius 1940 Act Mutual Fund

BMO Nesbitt Burns Ltd

KBI Global Resource Solutions CIT

Cornerstone Capital

Skellig Delaware Statutory Trust

LTW Investments LLC

The New Ireland Fund Inc.

The Park Foundation

Sun Life Global Investments

Sonen Capital LLC

University of Wisconsin Foundation

City and country of registered office (if applicable)

Amundi France Partner Networks- Paris, France

AP7 Swedish Pension Fund- Stockholm, Sweden

Cohesion Investments (Cayman) Ltd- Grand Cayman, Cayman Islands

KBI Global Sustainable Infrastructure Fund- Dublin, Ireland

KBI Eco Water Fund (ICAV)- Dublin, Ireland

KBI Global Resource Solutions Fund- Dublin, Ireland

KBI Water Fund- Dublin, Ireland

KBI Global Investors Aquarius Fund- USA

BMO Nesbitt Burns Ltd- Toronto, Canada

KBI Global Resource Solutions CIT- Pennsylvania, USA

Cornerstone Capital- Delaware, USA

Skellig Delaware Statutory Trust- Delaware, USA

LTW Investments LLC- Wilmington, USA

The New Ireland Fund Inc- Boston, MA, USA

Park Foundation- North Carolina, USA

Sun Life Global Investments- Toronto, Ontario

Sonen Capital LLC- Delaware, USA

University of Wisconsin Foundation- Wisconsin, USA

5. Date on which the threshold was crossed or reachedvi:

08.05.20

6. Date on which issuer notified (DD/MM/YYYY):

13.05.20

(only received for the attention of the company secretarial team of the issuer on 23 February 2021)

7. Total positions of person(s) subject to the notification obligation

% of voting rights attached to shares (total of 8. A)

% of voting rights through financial instruments(total of 8.B 1 + 8.B 2)

Total of both in % (8.A + 8.B)

Total number of voting rights of issuervii

Resulting situation on the date on which threshold was crossed or reached

6.7033%

6.7033%

108,283,000

Position of previous notification (if

applicable)

Below 5%

8. Notified details of the resulting situation on the date on which the threshold was crossed or reachedviii

A: Voting rights attached to shares

Class/type ofshares

ISIN code (if possible)

Number of voting rightsix

% of voting rights

Direct

(Art 9 of Directive 2004/109/EC) (DTR5.1)

Indirect

(Art 10 of Directive 2004/109/EC) (DTR5.2.1)

Direct

(Art 9 of Directive 2004/109/EC) (DTR5.1)

Indirect

(Art 10 of Directive 2004/109/EC) (DTR5.2.1)

GB00B64NSP76

7,258,503

6.7033%

SUBTOTAL 8. A

7,258,503

6.7033%

B 1: Financial Instruments according to Art. 13(1)(a) of Directive 2004/109/EC (DTR5.3.1.1 (a))

Type of financial instrument

Expirationdatex

Exercise/Conversion Periodxi

Number of voting rights that may be acquired if the instrument is

exercised/converted.

% of voting rights

SUBTOTAL 8. B 1

N/A

B 2: Financial Instruments with similar economic effect according to Art. 13(1)(b) of Directive 2004/109/EC (DTR5.3.1.1 (b))

Type of financial instrument

Expirationdatex

Exercise/Conversion Period xi

Physical or cash

settlementxii

Number of voting rights

% of voting rights

SUBTOTAL 8.B.2

N/A

9. Information in relation to the person subject to the notification obligation (please mark the

applicable box with an "X")

Person subject to the notification obligation is not controlled by any natural person or legal entity and does not control any other undertaking(s) holding directly or indirectly an interest in the (underlying) issuerxiii

x

Full chain of controlled undertakings through which the voting rights and/or thefinancial instruments are effectively held starting with the ultimate controlling natural person or legal entityxiv (please add additional rows as necessary)

Namexv

% of voting rights if it equals or is higher than the notifiable threshold

% of voting rights through financial instruments if it equals or is higher than the notifiable threshold

Total of both if it equals or is higher than the notifiable threshold

10. In case of proxy voting, please identify:

Name of the proxy holder

The number and % of voting rights held

The date until which the voting rights will be held

11. Additional informationxvi

KBI Global Investors Ltd is an investment management firm, based in Dublin, Ireland, which is regulated by the Central Bank of Ireland under MiFID II, and which provides discretionary portfolio management services to institutional investors. On the 1st February 2019, it purchased an additional holding in Costain Group on behalf of the shareholders listed in this form bringing the total holding to the 3% threshold.

Place of completion

Dublin, Ireland

Date of completion

13.05.2020