Leighton says worst is over on writeoffs LEIGHTON Holdings chief executive Hamish Tyrwhitt has pledged there is "absolutely zero" chance of the group having more writedowns like its painful experience on Airport Link and the Victorian Desalination Plant, and says the relationship with its major shareholder Hochtief is the best it has ever been. Mr Tyrwhitt said while Australia's biggest construction company would always have projects "that don't perform as we estimate," its risk-review and valuation processes had improved dramatically and it no longer had projects large enough to cause the same level of damage.