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Britain entered World War Two because of Germany invading Poland. But it failed to save the country from Stalin's clutches in 1945. So has a feeling of historic debt affected Anglo-Polish relations over the years?

I hear someone speaking Polish every day. On the train, in a shop, in the street. Ten years after Poland joined the EU, no-one knows for sure how many Poles live in the UK. The 2011 census estimated it at nearly 600,000.

But that doesn't include those who stayed after the end of World War Two, or their offspring - people like me. In total, the UK is probably home to a million or more people who regard Poland as their ancestral home in some way. Yet Britain and Poland have no long standing historical ties, like Britain and Ireland or Poland and France. The 1931 Census showed only around 40,000 Poles lived in the UK. Poland did not open an embassy in London until 1929. So how and why did we all end up here?

When Britain declared war on Germany on 3 September 1939 it did so for only one reason - Germany had invaded Poland, and Britain had guaranteed to support her ally, like it had supported Belgium in WW1. The diplomat and writer Sir Nicholas Henderson, himself a former ambassador to Poland, called it "a fatal guarantee".

About the author Marek Pruszewicz was born in the UK to Polish parents. His father escaped from the Germans during WW2 and joined Free Polish Forces based in Scotland. He settled in England after the war, one of tens of thousands of servicemen who did not return to Poland.

It was unprecedented. Britain had never given such a pledge to an eastern European country. There had never been a special relationship with Poland. Even Winston Churchill was amazed.

"His Majesty's Government have given a guarantee to Poland. I was astounded when I heard them give this guarantee," he told MPs in May 1939, when still a backbencher.

So why did Britain do it? The answer of course, had less to do with Poland, and much more to do with Nazi Germany.

In March 1939, Poland's southern neighbour Czechoslovakia fell apart. Adolf Hitler's German forces moved in, and Britain's Prime Minister Neville Chamberlain decided that Germany could not be allowed to threaten another country. Few people remember that Britain didn't just offer support to Poland. It also pledged to help Greece and Romania, should either of those countries be attacked.

Chamberlain called the assurances "first aid treatment" - an admission that the pledges were made in a hurry, with no thought to how such promises might be honoured. Britain hoped that would be enough - it was not. Germany attacked and defeated Poland in a few weeks. Britain declared war, but could not aid Poland.

The invasion

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Poland's defeat, followed by that of France, ensured that those Poles still able to fight found their way to Britain. Polish servicemen gained a reputation for bravery and ingenuity. One of the Polish squadrons in the RAF, 303 Squadron, recorded the highest number of kills of any squadron in the Battle of Britain.

The first cipher crackers to break Germany's Enigma code were not based in Bletchley Park but Warsaw. The Poles realised that mathematics held the key and made a vital disclosure of their working methods to the Allies at the start of the war.

But the Polish codebreakers were only officially honoured this year.

Image copyright Getty Images Image caption WW2 Polish servicemen "gained a reputation for bravery and ingenuity"

After the war, Clement Attlee's newly elected Labour government struggled to adopt a clear position on the Poles in Britain. "While we will not use force to compel these men to return to Poland, I have never disguised our firm conviction that, in our view, they ought to go back in order to play their part in the reconstruction of their stricken country," Foreign Secretary Ernest Bevin told MPs. Thousands did go home. But tens of thousands more refused to go.

The loss of eastern Poland to the Soviet Union, agreed at Yalta by Churchill, Roosevelt and Stalin, left thousands of Polish servicemen and their families with no homes to return to.

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Many Poles in the UK also feared - rightly - that the new National Unity Government in Poland was controlled from Moscow, and promises of free elections would not be kept.

Recriminations and bitterness followed. Some on the left of British politics, especially some trade unions, could not understand the reluctance of the Poles to return home. Pre-war Poland had not been a democracy - surely, ran the argument, a post-war Socialist Poland would be better?

One part of Britain where feelings ran high was Scotland, where many Polish units had been based throughout the war. "There was a lot of name-calling by the left including the communists. From playing a vital role in the defence of Britain, being the most loyal of Britain's allies, Polish officers now found themselves being called fascists," explains Robert Ostrycharz, a researcher of Polish-Scottish extraction. "I think that was due to them being fiercely anti-Communist and anti-Soviet - while those that made the accusation were very much pro-Soviet."

In early 1946 a conference of the Amalgamated Engineering Union passed a motion, sponsored by Scottish delegates, urging that all Poles be demobilised and returned to Poland. The Glasgow Herald denounced the motion as "stupid" and attacked "the hostility expressed towards the Poles by an intolerant minority in Scotland".

Image copyright Getty Images

Britain's Polish population - in numbers

Poles now constitute largest ethnic group in UK (after Indians) - 1% of population - more than Irish-born residents

Census in 2011 counted 579,000 Poles living in England and Wales

In 2013 Polish women gave birth to 21,275 children in the UK

But other slights followed. The Allied victory parade through London in June 1946 featured representatives from all the victorious armies - but not Poland's. Polish soldiers in Britain were not invited to take part. Those who commanded Free Polish forces also felt the wrath of the new communist-dominated leadership in Poland. In 1946 it stripped dozens of Polish commanders of their Polish citizenship, effectively making them stateless.

One of those men was General Stanislaw Maczek, commander of the Polish 1st Armoured Division, which had helped to seal in the defeated German armies in Normandy. Denied a country and a military pension, Maczek got a job as a barman at a hotel in Edinburgh to support himself and his family.

But as it became clear that eastern Europe was under Soviet hegemony, things changed for the Poles left in Britain. The Polish Resettlement Act - the first ever mass migration act of its type passed by Westminster - offered them help to settle into civilian life in the UK and eventually British citizenship.

Resettlement camps were set up across the UK to house Poles and their families. Some remained open for decades. The very last one, Ilford Park in Devon, is still open and still run by the Ministry of Defence, as a home now for nearly 100 elderly Poles.

By 1951 the UK census showed the number of Polish-born immigrants had quadrupled since before the war, to more than 160,000.

Image copyright Getty Images Image caption A Polish pilgrimage takes place annually in Aylesford in Kent

Over the next four decades the Polish community in the UK put down solid foundations.

And when Poland led the revolution in Eastern Europe with the rise of the Solidarity trade union, the UK was quick to pledge its support and resurrect the memory of the wartime alliance.

"It was the invasion of your country that brought Britain into the last war. The Polish Government came to London to carry on the fight for liberty. Many of your compatriots fought alongside us," Prime Minister John Major reminded Lech Walesa when he became the first ever Polish president to visit Britain in 1991. And he was clear that the UK wanted to see Poland as part of the European Community. "I have no doubt that, if you want it, you will become full members of the Community in the not very distant future."

It was to be another 13 years before Poland joined the EU, but when it did in 2004, the UK was one of only three member countries to allow Polish workers unrestricted access from day one. Just before that decision was announced, Prime Minister Tony Blair used a joint press conference with his Polish counterpart in November 2002 to once again revive the spirit of the Anglo-Polish wartime alliance. "Poland and Polish people, particularly Polish servicemen, made enormous sacrifices during World War Two and fought alongside British troops and it is particularly poignant and I think right that today Britain and Poland are working together to create the new Europe."

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After that, the number of Polish-born people in the UK rose from fewer than 100,000 before EU accession to more than 500,000 by the 2011 census - as the lack of restrictions on working and an already well-established Polish community attracted a huge influx. In 2004, Poles were the 13th largest foreign national group. By 2008, they were the biggest.

The effects were also cultural - the Polish plumber became a common stereotype and Polish shops popped up in British cities. By 2008, 44 million pints of Lech and Tyskie, Poland's two leading beers, were being sold annually in the UK.

Most of the EU did not open its doors to Polish workers in 2004. So was Britain's open door policy a legacy of comradeship in WW2?

It seems unlikely. For a start it wasn't just Polish workers being allowed in to the UK in 2004. The rules were relaxed for citizens of seven other European countries too - Czech Republic, Estonia, Hungary, Latvia, Lithuania, Slovakia and Slovenia. In other words, the decision was not about guilt or gratitude but economics, says Paul Lay, editor of History Today.

There was a philosophical consistency about Britain's position, says Lay, as the UK has a tradition of opposing protectionism. And in 2004 there were good practical reasons for the move. Britain was in the middle of a boom and needed skilled workers to fill its vacancies, says Lay.

A diplomat might go further - the UK has often been credited with having a long-held strategic aim of enlarging Europe to move its centre of gravity away from the "federalist core" - usually taken as France, Germany and the Benelux nations.

Famous Britons of Polish descent

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Tracey Ullman - film and TV comedy actress. Her father was a Polish soldier evacuated from Dunkirk in 1940

Sir John Gielgud (1904-2000) - one of the most famous English stage actors, his great-grandmother was a celebrated Polish actress

Ed Miliband - the Labour leader's grandparents came from the Polish capital, Warsaw

The high number of Poles created pressures and fears. At first there was praise for "hardworking" Poles, but as the stereotype of the Polish plumber and builder became common shorthand, there were fears over wages being undercut for indigenous workers. Gordon Brown even went so far as to promise "British jobs for British workers".

Newspaper headlines have sometimes suggested a remorseless tide of newcomers, such as a 2013 Sun story implying that most of Lodz's population had moved to the UK.

And during 2013 police arrested 585 people for hate crime against Poles.

Image copyright Getty Images

YouGov's "poll of Poles" in January this year showed that Polish people, in general, are positive about the UK. But many feel British people are not so positive about them.

There seems to be a generational split, with 72% of Polish people aged 25-34 holding a positive view about the UK, but only 30% thinking Britons had a positive view of them. For older people things are more in balance. Of those aged 55-plus, 63% had a positive view of the UK, while 49% perceived a positive view of Poland from British people. Meanwhile British people - by 38 to 29 % - thought that Poles had had a beneficial impact on Britain, according to a YouGov poll in September 2013. So one might judge that anti-Polish sentiment is not widespread. And you can argue that much of today's most negative coverage of eastern European immigrants is reserved for Romanians.

At some deep level Britain may still feel a debt to Poland over the war. But it's not something that the man in the street thinks much about, says Lay. Things have moved on.

But 75 years after Britain took the fateful decision to fight because of Poland, the repercussions of that alliance are arguably stronger now than ever - think about that the next time you pass a Polish delicatessen.

Additional reporting by Tom de Castella

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