The move will give the $1bn turnover contractor a 15% stake in Costain’s business.

Costain this morning confirmed that its joint book-runners had successfully placed all 167m shares in the fund raising.

Alex Vaughan, chief executive officer, said: “We are pleased to have secured significant support from investors for this fundraising.

“With a stronger balance sheet and the positive long term outlook for UK infrastructure, Costain will be better placed to benefit from the significant market opportunity in front of us.“

Around 80% of the funds are being raised through a firm placing, while the remaining £20m is to come through an open issue of shares at a discount of 20% to the 75p share price yesterday.

Banking partners have agreed, subject to the completion of the capital raising, to extend Costain’s existing debt facilities, which are due to be renewed next month,  to September 2023.

Its new major stakeholder, Dubai headquartered construction group ASGC, said it saw significant long-term, structural growth opportunities in UK infrastructure.

Established in 1989, the business employs 17,000 staff focussed on delivering turnkey special projects in the UAE, and more recently Egypt and Africa.

ASGC is delivering landmark projects such as the Coca-Cola Arena in Dubai, expansion and improvement works for Dubai International Airport, expansion of the Dubai Mall, the Waldorf Astoria on the Palm Jumeirah as well as several pavilions for Dubai EXPO 2020.

Costain’s board also this morning set out its worst-case scenario planning for the impact of the pandemic.

Based on a six-month disruption due to lockdown and new social distancing measures, Costain forecasts a 56% reduction in profit from complex projects, a 10% reduction in profit from higher-margin consultancy, and a 43% fall in profit on new work obtained.

It said that based on this scenario, the £100m cash-raising and access to existing facilities it would have sufficient working capital for 12 months.

Costain said most of its clients were pressing ahead with projects under new safe working procedures.

The group has also made reductions to its cost base, deferred capital expenditure, PAYE and VAT payments. The board and senior leadership team has agreed a 30% reduction in salaries for up to three months.

Last month HS2 granted Costain’s joint venture company, Skanska Costain Strabag, notice to proceed to full detailed and design construction of Phase 1 of the HS2 railway in area south as part of the main works contract.

Also Costain was awarded a £210m design and build contract by Highways England to upgrade an existing section of the A30 north of Truro, Cornwall, it was also named one of the six partners in the £4.5bn Smart Motorway Programme Alliance.