This is how it starts: the drip, drip of abuses gathering pace until we realise that we are not safe either. I arrived in Britain aged four with no knowledge of what laws entitled me to start a new life here. My father was born in British Somaliland and obtained his first UK passport at the age of 22; he had lived in Yorkshire for 40 years by the time we joined him, and had made a conscious decision to settle in Britain rather than all the other countries life as a merchant sailor took him to. He had lived through other “hostile environments”, but thought this country respected the law and would offer us a stable home.

Now it seems that people like me, who arrived legally as children, have been made homeless, deprived of urgent healthcare and benefits, as well as detained and deported. Slurs and fake news regarding refugees and migrants have reached such a pitch that any harm coming to them is often seen as deserved – their very presence seen as burdensome, dangerous and offensive. The reaction to the Windrush scandal has challenged some of that rhetoric as the now elderly “migrants” are culturally familiar (unlike those of Muslim heritage), are perceived to have “earned” their citizenship, and clearly do not present a danger to anyone. The fact that the Tory party saw their detention and deportation as politically advantageous shows how far public opinion had gone in terms of immigration.

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Some present these attitudes as a recent response to EU open borders or the much greater proportion of minority ethnic people in British cities, but this xenophobia has much older manifestations. Almost a century ago, after the 1919 race riots (a misnomer which implies a parity of power and violence) rocked the tiny Black and Asian communities in UK port cities, the government’s chief immigration officer commented that the presence of colonial seamen (from the British empire) was socially undesirable and that “it would be better to place these men in concentration camps”.

Six years later the aliens’ order was used to detain and deport “coloureds” even if they had a right to be here. In 1972, faced with the arrival of thousands of Ugandan Asians with UK citizenship, the government tried to find them an alternative home in the Falklands or the Solomon Islands. Women arriving from India and Pakistan to legally join their husbands could be subjected to virginity tests at British airports until 1979.

The mechanism through which immigrants are dehumanised became clear to me after the Grenfell fire. Once the immediate shock of Britain’s worst fire since the second world war wore off, there quickly appeared a desire to blame the victims rather than the authorities. Grenfell Tower, according to former residents, had been a stable, sociable community of people from all over the world, nearly all of them in work or retired. The image drawn afterwards was that the tower block was “a nest of illegals” – to use a phrase defended on morning TV by Ukip’s former leader, Henry Bolton – with so many “illegals” living there that the police hadn’t been able to identify them all.

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This story is repeated so often that it is taken for fact, despite the reality that all 72 victims have been identified, including those for those whom only “forensic anthropology and secondary supporting evidence” could be used. None of them were “illegal”: but even if they were, would they be less worthy of our grief? What about the 17 children (all born of migrants) who died there? Should we ask to see their birth certificates and school reports before admitting they didn’t deserve to die?

I was originally dismissive of the idea that there had been any substantial change in attitudes or behaviour surrounding the Brexit vote. I remembered the Combat 88 neo-Nazi stickers plastered around the council estate I grew up in in the early 1990s; the two Somali mothers in neighbouring blocks who had been harassed out of their homes; the worry I felt for my brothers after Stephen Lawrence was murdered and his killers allowed to walk free. This xenophobia has always been here and it’s something I have generally learned to ignore for my own wellbeing; but now I feel it is growing in both intensity and shamelessness.

There appears to be a hardening in social attitudes towards all marginalised people; but the individuals at the bottom of the pecking order remain those with uncertain immigration statuses, often homeless and unable to work.

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While at university I regularly visited the nearby Campsfield House detention centre, where I was paired with a young detainee who had escaped political repression in Ghana. He was in limbo but did not report any abuse or mistreatment. The situation for those in similar circumstances is drastically different now. In Yarl’s Wood, at least 50 women recently went on hunger strike to protest against indefinite detention as well as the absence of basic necessities such as underwear and warm clothes.

Last year deaths in immigration centres in England and Wales reached their highest recorded level, and the continued use of restraints and segregation on individuals with complex medical issues as well as mental health needs has led the British Medical Association to call for the closure of all detention centres.

This is how it starts: we learn to ignore what seems overwhelming or unresolvable, we lower our expectations and hope we’ll be left alone. In the meantime, the most vulnerable among us are exposed to the violence and spite of those in power. Seventy years after the arrival of the Empire Windrush at Tilbury, it is a deep shame that we need to reaffirm our right to be here; that no matter how long we stay here or what we contribute, we remain eternal strangers.

• Nadifa Mohamed is a British-Somali novelist