UK demographics

Mark Steyn quoting the UK's Office of National Statistics:

In 2010, a quarter of births were to mothers born outside the UK, according to the ONS…
If a quarter of all babies born in England and Wales are to foreign mothers, then we’re experiencing the biggest change in our demographic identity since the Anglo-Saxon invasions of the fifth century. Future historians will regard this as the major development in early 21st-century British history…
Nothing like this has happened before. Please pay no attention next time a Left-wing historian pops up on TV to romanticise the arrival of the Normans, Huguenots, Eastern European Jews etc. These were significant influxes, but Great Britain has never been “a nation of immigrants”. Even cosmopolitan London has witnessed nothing remotely comparable to the population shift recorded by the ONS statistics. More than half of all babies born in the capital in 2010 were to foreign mothers; in the borough of Newham more than three quarters of all new mothers were born abroad.
A lot of people reading Ed West will say: “Well, so what? What’s the problem?” That’s fine if you want to turn some of the oldest nation states on the planet into an ongoing experiment. Maybe the experiment will work out fine, maybe it won’t. But, given that the nations most enthusiastically embarking on it are responsible for 90 per cent of everything the modern world takes for granted, you’d think more people might at least give some thought as to whether the gamble is worth it.