The firm’s executive chair said HS2’s costs had risen so much over the past decade because of poor cost estimating, changes to the project’s scope, some poor delivery and the impact of inflation. He added that decisions to delay parts of the project for cashflow reasons, could end up meaning they cost more, and that the Covid pandemic had added £500m to £600m. Sir Jonathan also said HS2 trains will travel more slowly than existing Pendolino trains when they travel on conventional tracks between Birmingham and Manchester, because they cannot tilt on bends.