Transaction in Own Shares

Summary by AI ^BETAClose X

Costain Group PLC has purchased 295,070 ordinary shares between April 22 and April 28, 2026, as part of its share buyback program, with weighted average prices ranging from 179.19 pence to 185.73 pence. These shares are intended for cancellation, and following this, the company's total issued ordinary shares will be 268,132,367. The aggregate volume of shares purchased across various venues during this period was 285,029, with an overall weighted average price of 181.87 pence.

Disclaimer*

Costain Group PLC

29 April 2026

Costain Group PLC

Transaction in own shares

Costain Group PLC ("Costain") announces that, in accordance with the terms of its share buyback programme (the "Programme") announced on 10 March 2026, it has purchased the following number of its ordinary shares of 1 pence each ("Ordinary Shares") on the London Stock Exchange through Panmure Liberum in the period from 22 April 2026 to 28 April 2026.

Date of Purchase	Number of ordinary shares purchased	Weighted average price per day (pence)	Highest price per share (pence)	Lowest price per share (pence)
22 April 2026	57,000	185.73	184.60	186.60
23 April 2026	55,789	183.71	182.40	185.20
24 April 2026	53,755	180.34	178.60	183.00
27 April 2026	56,000	180.61	178.60	181.80
28 April 2026	62,525	179.19	177.60	180.80

The Company intends to cancel the purchased shares. The Company does not hold any ordinary shares in treasury.

Costain has now purchased 1,582,528 Ordinary Shares in aggregate for cancellation under the Buyback Programme. Following settlement of the above purchases and cancellation of the purchased Ordinary Shares, the Group's total number of Ordinary Shares in issue will be 268,132,367 Ordinary Shares.

In accordance with Article 5(1)(b) of Market Abuse Regulation (EU) No 596/2014 (as it forms part of the law of the United Kingdom by virtue of the European Union (Withdrawal) Act 2018, as implemented, retained, amended, extended, re-enacted or otherwise given effect in the United Kingdom from 1 January 2021 and as amended or supplemented in the United Kingdom thereafter) a full breakdown of the individual trades made by Panmure Liberum on behalf of the Company as part of the Programme can be found at:

http://www.rns-pdf.londonstockexchange.com/rns/4128C_1-2026-4-29.pdf

Aggregate information:

Venue	Volume-weighted average price (pence per share)	Aggregated volume	Lowest price per share (pence per share)	Highest price per share (pence per share)
BATE	181.82	113,347	177.60	186.60
XLON	181.93	147,882	177.60	186.40
CHIX	181.70	18,000	178.20	186.60
TRQX	182.20	5,840	178.60	186.00

Enquiries:

Investors and analysts

Matt Jones, Costain

Matt.Jones@costain.com

+44 (0) 7860 922 341

Financial media - Headland

Andy Rivett-Carnac

Charlie Twigg

costain@headlandconsultancy.com

+44 (0) 7968 997365

+44 (0) 7946 494568

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