By Richard Bilton
The clues are there if you know where to find them. Walk around Slough's estates and look in the back gardens.
There are buildings here you are unlikely to see anywhere else in the country.
These are Slough's 'sheds with beds'.
In some areas, row upon row of them. Lines of small houses tucked away behind the main homes.
And inside them are the people who are transforming this place. A new workforce.
HOW WE COUNT MIGRATION
International Passenger Survey
NHS patient records
Births and deaths
Worker Registration Scheme
So many that these illegally rented out sheds and garages are needed to house them all. They have been swept here by border changes across Europe and are now testing how we deal with mass immigration.
Slough is a success story. A manufacturing town with a booming economy. Positioned just outside London and down the M4 from Heathrow.
Its factories and production plants have always attracted a large number of immigrant workers.
"I came here in 1948. I wanted to work in Britain, and I got a job in the brickworks," said Fred Szymaczack, a Pole who says things were very different when he came to Slough.
"When I arrived it was much stricter. The government knew how many people were coming to work here. Now, there's too many. The town can't cope."
The expansion of the European Union in 2004 has had an enormous effect here as it has across Britain.
Local Polish community leaders say as many as 10,000 Poles have arrived in Slough in three years.
Walk down the High Street and you can literally hear the languages and accents that are changing the make up of this town.
The problem is there is no accurate way of recording that change.
When it comes to migrants arriving in our towns, it seems we've lost the ability to count.
The government's estimates show Slough's population is decreasing, while the council in Slough reckons it is growing so fast that about one in ten people here are simply missing from the books, not accounted for. And that has a direct consequence for everyone living here.
That is because the government uses the population figure to decide how much money it gives the local council every year.
That money funds three quarters of the services provided by the council. If the population estimate is not accurate, then neither is the pay-out.
'Chuck them out'
Andrew Blake-Herbert, director of finance for Slough council said: "Over the last three years, we've already lost £5 million worth of funding and if the inaccurate population statistics aren't corrected before the next census, we stand to lose up to £15 million worth of funding"
Of course, most of the migrants are working and paying tax but all that money goes to the exchequer, it does not come to Slough.
All that does comes here is an increased pressure on services. So, that means the Council Tax in the town is as high as it can be.
Cuts are on the cards and people are not happy.
The UK's population is estimated to be more than 60 million
But there is a bigger danger. This is a town that has known decades of tolerance.
New communities have always been accepted but now some of the older migrants are saying things have to change.
I went for a walk through Chalvey, an area of Slough that has become home to hundreds of new arrivals. One resident, Mohammed Choudary Sr told me if more money does not come from the government, the council has to get tough.
"Chuck them out. It's simple. Just don't let them come in. Don't give them housing. Tell them to go to other places".
The stakes are high and the government accepts there is a problem.
The Immigration Minister, Liam Byrne issued this statement to Panorama.
"We think it's utterly important that the wider - often social impacts - are taken into account before decisions are made.
Next year we're introducing an Australian style points system which has worked well there.
Before we decide how many points would-be immigrants need to come to Britain, we'll be looking at independent evidence from the Migration Impacts Forum on these wider impacts.
Migration is important to the British business community, but businesses shouldn't be the only voice in the debates. Communities count too."
Of course, any points based system would not apply to migrants from Europe, like Slough's Poles.
The current flawed system means people living here, hear the government say the town's population is falling while all around - from housing and packed schools, through to increased refuse collection and rising crime rates - the signs are it is on the up.
And what is happening in Slough is being repeated across the country. In towns and cities across the land we simply do not know how many migrants are arriving.
For more and more communities the numbers no longer add up.
Panorama - Immigration: How we lost count was on BBC One at 2030 BST on Monday 23 July 2007.