When I arrived in the Home Office with Theresa May as her adviser in 2010, we discovered that official impact assessments – the Government’s process of weighing up the pros and cons of policy – had long been skewed in favour of higher immigration. Because a larger population meant a larger economy, and the assessments assumed that was what Britain needed, they failed to consider the economic effects of immigration on a per-person basis. And they excluded costs like the impact on existing workers’ wages, infrastructure, and public services.

When we commissioned the Migration Advisory Committee to review these assessments, their findings surprised even us. Examining non-European immigration between 1995 and 2010, they found that for every 100 foreign-born workers employed, 23 British workers had been displaced from the labour market. The response to the report was typical of the immigration debate. Advocates of lower immigration pounced on the findings with enthusiasm. Supporters of higher immigration denigrated the report and pointed to other evidence that suited their views.

I do not pretend to know whether all immigration, added together, always displaces local workers or reduces wages. Immigrants vary from brain surgeons to semi-literate octogenarian grandmothers. They come during boom years, recessions and everything in between. And they join an already complex labour market comprising millions of people.