The firm acquired the stake for £25m back in May 2020 as part the UK contractor’s £100m fund raise.

The ASGC shareholding, which was sold at a 13% discount to yesterday’s share price of 105p, is understood to have been placed with institutional investors.

A Costain spokesperson said: “We note that the sale by ASGC was increased from their original proposal, reflecting strong demand from other institutions for our shares including existing holders increasing their positions. This recognises the continued strong performance of the business, high volume of forward work and on-target margin growth.”

Costain shares were down 7% in the first few hours of trading after the announcement.