As the inestimable Frank Field reminds us, the Home Office- and indeed the entire government - has long inhabited a parallel universe in terms of immigration.
"When the EU expanded to 25 members in 2004 the UK, Ireland and Sweden were the only countries which decided not to restrict people from the new member countries - notably Poland - taking jobs.
At the time the UK government predicted 13,000 workers a year from the new EU member countries would move to the UK for work, but the actual figure of registered workers was about 329,000 in 18 months."
Out by a factor of twenty. And that's only the new Europeans that have bothered to register.
But as Field says, this is much more important than just hopeless forecasting. It is by no means clear Britain can absorb such massive inflows:
"It is only because the BNP are so inept that the debate has not taken off...mainstream politicians should address immigration "before the BNP stumbles on somebody with talent...We are living on borrowed time. We can not continue on the assumption that the BNP will present leaders which turn off most voters, even if what they are saying is important."
PS Mass immigration is clearly bad news for native plumbers, farm workers and cleaners. But is it even good for the economy overall? Although the conventional wisdom says yes, it's by no means clearout. See the analysis on Migration Watch.