ISG is one of the biggest players in prison upgrade and new construction work as the country faces a chronic shortage of cells with offenders being released early from overcrowded jails.

The contractor started work earlier this year on a combined £135m upgrade for HMP Guys Marsh in Dorset and HMP Liverpool.

Its £79m project at Guys Marsh was due to deliver two house blocks, one with 122 cells, the other with 59, to increase capacity by 31%.

At HMP Liverpool its £56m is for a full overhaul to support the prison’s proposed change in status from a Cat B to a Cat C facility.  

ISG is also lined-up as main contractor for a a £300m new Category C super prison in Buckinghamshire at a site next to the existing HMP Springhill and HMP Grendon.

ISG is one of the biggest contractors by spend with the Ministry of Justice and has places on major frameworks including its £1bn New Prisons Programme and £2.5bn Constructor Services Framework.

Figures compiled by construction data specialist Barbour ABI show ISG is currently onsite on projects worth £1.7bn with a further £1.9bn of work in the pipeline.

Its biggest current contract is the £150m fit-out of Google’s new headquarters building at King’s Cross.