London (CNN)On Monday, Britain celebrates Windrush Day, honoring a generation of Caribbean immigrants who moved to the UK in the late 1940s at the invitation of the government.
In recent years though, the British government's treatment of those individuals -- known as the Windrush generation after the Empire Windrush passenger liner that brought some of them across the Atlantic -- and their descendants has been the subject of a massive scandal.
Who are the Windrush generation?
The people who became known as the Windrush generation were invited to Britain to lay roads, drive buses, clean hospitals and nurse the sick, helping to rebuild the country after the devastation of World War II.
They first arrived aboard the Empire Windrush in June 1948, landing at Tilbury Docks, about 20 miles from London. These voyagers -- many of them from Jamaica -- were the first large group of Caribbean migrants to arrive in the UK.
They came to symbolize the seismic demographic changes in Britain that started after World War II and continued into the late 20th century, as hundreds of thousands of people arrived from former British colonies, known as the Commonwealth.
What was the scandal about?
The Windrush generation migrants arrived in Britain legally. Until a new immigration law came into force in 1973, Commonwealth citizens and their children had the automatic right to live and work in the UK. Many did so, without any need for additional documentation.
In late 2017, however, a raft of cases were reported in which individuals who had arrived in the UK from Commonwealth countries before 1973, and sometimes their descendants, were struggling to prove their citizenship status under tough new immigration laws billed as a "hostile environment" policy.
Many don't have the required documentation because they had never been required to have it before. Some said they had been refused medical care, denied housing and deported or threatened with deportation.
What was the government's reaction?
In April 2018, Britain's then-Prime Minister, Theresa May, apologized for her government's treatment of some Caribbean immigrants and insisted they were still welcome in the country.
A year later, then-Home Secretary Sajid Javid announced a compensation program for people who had been wrongfully detained or removed from the UK.
However, the program was widely critic