Many public projects have strong advocates. On several occasions there was evidence that costs had been aimed at the figure necessary to obtain approval, rather than robustly estimated and justified by the projects' benefits. Similarly, once ceilings were imposed on project costs, additional works were obtained through waiting for successive budget years. The project is most vulnerable to this bias at the business case stage. However, it can persist to the contract award stage especially where scope definition is incomplete or not functionally expressed, leading to changes in scope and cost. Once a project has gained momentum (especially politically), it is sometimes difficult to consider an alternative and so ultimately, the project goes ahead despite knowingly underestimating project costs and time.