Political crises often have short shelf lives; as the floodwaters of one Boris Johnson gaffe ebb, so another tsunami of poor decision-making (usually, again by Johnson) comes crashing over the harbour. But the Windrush affair is no mere scandal. What we have witnessed are the consequences of a Home Office culture that is rotten to the core – and it will take more than a single resignation and a subtle tweak in rhetoric to fix it.

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It is only right that Amber Rudd was compelled to resign. It’s one thing to get caught out, quite another to get hung out to dry by your own correspondence. However, it is vital to note that her departure from the government’s front bench is due only to having “inadvertently” misled the home affairs select committee. The underlying causes behind the detention, exclusion from public life, and potential deportations of British citizens of colour went unremarked in Rudd’s resignation letter.

So what of her successor as home secretary, Sajid Javid? If we are to be led by certain voices from the liberal commentariat and even Labour councillors, we ought to celebrate the appointment of Britain’s first home secretary from an ethnic-minority background as a victory for anti-racism. Indeed the MP for Bromsgrove took pains to stress in his first Commons appearance as home secretary that his heritage lends him a unique perspective on and empathy with the plight of Windrush generation migrants: “Like the Caribbean Windrush generation, my parents came to this country from the Commonwealth in the 1960s [...] I thought that it could be my mum, my brother, my uncle or even me.” In keeping with this personal touch, Javid rejected the polarising language of the “hostile environment” in favour of a “compliant environment”.

I’m sure that Javid is perfectly sincere in his statement of affinity for the Windrush migrants. However, one is compelled to turn to his voting record in order to assess what this shift in tone might mean in policy terms.

Javid has supported every single piece of hostile environment legislation that’s been put before him, from supporting the detention of pregnant women and vulnerable people in immigration removal centres, to backing the right-to-rent policy that has resulted in 51% of landlords reporting that they are less likely to let properties to those they perceive to be migrants. Most damningly, the promised immigration amnesty for Grenfell survivors (under Javid’s former remit as communities minister) has been severely corroded by lack of trust in the process. Few have come forward, and the inquiry risks being deprived of key witnesses if they are deported from this country.

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Furthermore, the phrase “compliant environment” is so far devoid of any meaningful content in policy terms, other than not involving the reinstatement of a clause protecting longstanding Commonwealth-origin residents in the UK, which was removed from the statute books by the Immigration Act 2014. The medical gatekeeping that saw Sylvester Marshall (previously referred to as Albert Thompson in the Guardian) denied cancer treatment for six months might be here to stay – along with the ongoing planned deportation of Windrush generation migrants, and the continued detention of sexual assault and torture survivors.

Perhaps the discovery of personal Commonwealth heritage is a relatively recent phenomenon for Javid. Or maybe, and stay with me here, the mere possession of melanin is not a cast-iron guarantee that a politician will err on the side of justice.

But ultimately there’s only one person responsible for the Windrush affair, and the calamitous consequences of the hostile environment policy: Theresa May. Over the past eight years, hostile environment logic has been written through home office DNA.

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May’s tenure as home secretary was marked not only by her embrace of harsh rhetoric, but also structurally encoding an unforgiving, target-driven culture. A bonus of £5,000 to £10,000 was given to the head of immigration enforcement for delivering internal targets, including removals from the UK. Placed alongside May’s personal commitment to “deport first, hear appeals later”, this pay structure fundamentally undermines the integrity of our entire immigration system. How can anyone – whether a British citizen or a foreign national – have any faith that their case will be heard with respect for due process, when civil service oversight is corroded by the offer of a cash incentive?

We have reached a point of mutually exclusive choosing in British immigration politics. We could continue with May as the guiding hand in home affairs, and make our peace with an unworkable, immoral and unjust policy immiserating the lives of migrants who have enriched this country. Or we could reject the Tory transformation of the Home Office into the Ministry of Institutional Racism – and commit to an immigration strategy that widens avenues towards citizenship; recognises the immense contributions of Commonwealth migrants to British society; and focuses its energies on regularising the tax arrangements of financial elites, rather than excluding working class people of colour from the NHS.

A better and fairer policy is possible; a transformed Home Office working culture is imperative. And it must begin with the end of May.

• Ash Sarkar is a senior editor at Novara Media