Wendel, the listed French investment company, will on Thursday announce it has increased its stake in Saint-Gobain from 18 per cent to 20.6 per cent – close to its limit allowed under a pact agreed with the building materials group last week.

Publishing its full-year results on Thursday, Wendel will also record a €345m ($544m) charge to cover the cost of financing and hedging its €4bn stake in Saint-Gobain, which is two-thirds funded with debt and has fallen sharply in the past six months. The charge will be more than offset by the exceptional gain of about €800m Wendel made last year from floating Bureau Veritas, the inspection and testing company.