Does this sound familiar? A political backlash against the wave of immigration; East Europeans competing with native Londoners for unskilled jobs, pushing up rents, and swamping the schools.

As one Conservative London MP put it: “English families are turned out to make room for foreign invaders. The rates are burdened with the education of thousands of foreign children.”

Actually the MP — Sir William Eden Evans-Gordon — was speaking in 1900, and he meant Jews. They, and London, did fine. It grew, and it boomed. We even hosted a successful Olympics in 1908.

When my parents moved to London in the early Seventies, immigration was at a low ebb. The result: the inner-city population shrank by 20%. It’s easy for today’s Londoners, living in one of the world’s great global cities, to forget that only 30-odd years ago London (like New York) faced falling population, rising crime, and no obvious replacement for vanishing manufacturing jobs; it seemed doomed to permanent decline.

Globalisation and, central to that, immigration, saved the city. People born abroad now make up half of Londoners between 20 and 40. Immigrants form an essential part of the workforce at all skill levels — from supermarkets and sandwich shops to law firms, tech start-ups and research institutes like my own. London’s recent economic growth has been driven by immigration; without immigration it would come to a screeching halt. Immigration makes London, by far, the most productive part of the UK.

What about the downsides? Congestion and pressure on housing, definitely. But let’s not exaggerate. I live in Islington, now the most densely populated borough in the country. But Islington’s population has only just regained its 1971 level. A century ago, twice as many people lived here.

Schools? London schools make a virtue out of the necessity of coping with high turnover and many pupils for whom English isn’t a first language. They have improved so rapidly over the past decade that kids in our poorest neighbourhoods do better than the average pupil living outside the capital.

David Goodhart, who is speaking in the Evening Standard debate, claims London’s diversity conceals “sundown segregation; people mixing during the day but going home to quite separate neighbourhoods”. Really? One in eight London babies is of mixed heritage. Not only do most Londoners not go home to ethnically separate neighbourhoods, many don’t go home to separate beds.

To say that immigration is essential to London — economically, socially, and culturally — is simply stating the obvious. The question is how we manage immigration in London’s interests. Here’s where recent policy has gone in entirely the wrong direction.

We attract hundreds of thousands of foreign students to this country every year. Some want to stay — get a job, start a company, maybe make a life. By definition, these are people who not only have higher education but also good English and, in most cases, the desire and ability to integrate into this country.

So what do we do? We kick them out — in pursuit of the Government’s economically illiterate attempt to reduce migration to the “tens of thousands”. Sir Andre Geim, the Russian-born Nobel prizewinner, claimed that the identification of graphene would “probably not have happened if I had been unable to employ great non-EU students”. Actually, he’s wrong. Of course it would have happened. Somewhere else.

What about European migrants? Recent migrants from the European Union have made a net contribution of about £15 billion to the public finances over the last five years. That is how much more they have paid in taxes than cost us in benefits and public services. So much for “benefit tourism”. Without them, we would have to pay higher taxes or endure worse public services. And research here at the National Institute of Economic and Social Research shows that the long-term economic impacts are even bigger.

Reducing immigration by keeping out skilled workers, stopping students from staying on and generally promoting, in the Government’s words, a “hostile environment” for foreigners is economic masochism. The UK — especially London — simply cannot be “open for business” and closed to immigrants.

So the economics are clear enough. But for most of us, this is intensely personal. I’ve lived here since I was five. But my “family” has roots in Chicago and Gujrat, in rural France and in New York. We are Londoners; without us – without you, reading this – it wouldn’t be London.

Jonathan Portes is director of the National Institute of Economic and Social Research