Alan Goodrum says official figures supporting the new High Speed Rail are impossible to verify.

Forecasting is a notoriously unreliable business. You might get four days with the weather. Beyond a week can be difficult in the world of politics. Three years is long term in many businesses. And as planners have learnt, the more you move away from the relative certainties of population forecasting and households to employment and the economy, the more hazardous things get.