32 In spite of London Underground's thoroughness described above, our analysis has shown that there are limits, which London Underground recognises, to the weight that can be put on the figures emerging from the Comparators exercise. These derive from three areas:
■ there is inherent uncertainty in modelling the costs of the London Underground infrastructure over 30 years;
■ the financial models alone would provide only limited guidance to the most likely cost of a public infrastructure operation; and
■ the costs of public operation are influenced by the choice of financing scenario, including the availability and impact of bond finance and the costs of conventional public finance. Yet there is uncertainty about what some of these costs are and how they should be assessed.