The surge has come from eastern Europe
The Office for National Statistics (ONS) has published its most comprehensive assessment of the numbers of migrant workers in Britain.
It confirms the general picture of a recent surge in immigration.
The ONS concludes that opening the UK to workers from the EU accession countries "initiated what is almost certainly the largest single wave of in-migration that the British Isles have ever experienced".
In 2005, it says, one in 19 workers in Britain was a foreign national.
Up to now, debate on migration has been confused by a plethora of different statistical sources covering different groups, often with out-of-date figures.
But the official study by two authors from University College London, Professor John Salt and Jane Millar, draws together as much of the available evidence as possible for recent years.
The conclusions are not surprising. Last year, 400,000 foreign workers came to the UK, the largest ever number, taking the total foreign workforce to 1.5 million.
But is this the biggest influx in the history of the British Isles, as the authors claim?
"Probably", is the answer.
Look back to the Huguenots, protestants who fled France in the 16th and 17th centuries. They made up about 1% of Britain's population, and 5% of London's.
But there were only tens of thousands of Huguenots, spread across two waves a 100 years apart.
More recently, net immigration from the new commonwealth peaked at an annual 50,000 in the late 60s.
The Asians arriving after expulsion from Uganda by Idi Amin in 1972, numbered fewer than 30,000.
Of course, we don't know how long the current inflow of central Europeans to Britain will last, or for how long they'll choose to stay.
But clearly - perhaps thanks to advances in transport - migration moves quickly these days.