Last week's Brexit speech by the prime minister setting out her approach to leaving the EU swamped a simultaneous report from the Office for Budget Responsibility warning that the ageing population will be a major factor in driving up public spending by £156bn a year or from 35.8% of GDP in 2022 to 43.8% by 2066.

The OBR is not in the habit of producing alarmist reports. It has been accused of being too optimistic. Its 2010 Budget report predicted the deficit falling to 1.1% of GDP by 2015/16, whereas it is still on 4%, and total debt to be 67.4% of GDP that year, whereas it is actually 87%. So its latest annual Fiscal Sustainability Report for the next 50 years with its eye-watering figures for public spending deserves scrutinising. It projects health spending rising from 6.9% of GDP in 2021/22 to 12.6% by 2066/67 and the state pension increasing from 5% of GDP to 7.1%.