This is how they do it now. UK Border Agency (UKBA) officers go Walthamstow, they go to Kensal Green, Stratford and Cricklewood, to the bustling hearts of London's multicultural experiment, and they check your papers.

Burly, aggressive men stop passers-by as they walk into the tube station in a bid to find out their immigration status. Ordinary Londoners trying to get to work are subject to a humiliating and threatening ordeal.

Officers know their legal right to do so is highly questionable but they also know one of the great truths of human interaction: that when an official questions a minority, the law means nothing. They act with the confidence of the uniform, the unwavering assumption from the minority that the law is not on their side.

But one of the great things about this country is that the law is on your side. You have substantial rights and immigrations officials have very few.

Immigration officers' right to stop and question people away from ports of entry are governed by paragraph 2, schedule 2 of the Immigration Act 1971, as supported by the long standing judgment of Singh v Hammond. There are strong restrictions on what they can do.

Here is the relevant passage from chapter 31 of UKBA's Operational Enforcement Activity manual:

Before seeking to question someone, an IO [immigration officer] will need to have information in his possession which suggests that the person may be of immigration interest (that is there are doubts about that person’s leave status). The information in the IO’s possession should be sufficient to constitute a reasonable suspicion that that particular person may be an immigration offender. Any IO stopping and questioning an individual will need to be in a position to justify the reasons why they considered that threshold to be satisfied in that particular case. Any questioning must be consensual. The paragraph 2 power to examine does not include a power to compel someone to stop or to require someone to comply with that examination. Should a person seek to exercise their right not to answer questions and leave, there is no power to arrest that person purely on suspicion of committing an immigration offence.

This is a very high standard. It is illegal for an officer to conduct a speculative check on your immigration status. If you are a commuter simply going to the Tube station, you do not satisfy this standard. Demand to know why you are being questioned. If you do not receive a decent answer, inform the officer of your rights and walk away. You can walk away, because this is a free country.

This will be a threatening situation, with an unfriendly and often physically imposing officer. The reason they are being threatening is because they are hoping to scare people out of recognising their rights. It is a coup of charisma, of confidence. Don't let them do it. Hold your nerve.

When you first see the UKBA presence do not do anything which raises suspicion. This is referred to as "having an adverse reaction to an immigration presence". Doing so gives the officers reasonable suspicion.

Do not change the speed of your walking or suddenly change direction. Maintain a steady pace. Do not hang back from the barriers. Do not behave confrontationally or aggressively. Enter into the conversation willingly, and then state that you are aware of your rights and can walk away unless the officer can give a reason for having reasonable suspicion of your status.

Use your phone to film the entire encounter. Any officer who speaks to you must identify themselves verbally and by producing a warrant card. They must explain their reason for questioning you.

At this point ask them what gave them reasonable suspicion to have stopped you. They must tell you that you are not obliged to answer any questions. They must tell you that you are not under arrest and are free to leave at any time. If they fail to do any of these things, tell them.

Make sure you clearly record the identification number of the officer. Sometimes this will be covered up or not present – it's a common tactic. Insist on knowing the number before you cooperate with the officer. If at any point you decide to leave they cannot pursue you unless they have sufficient basis to arrest you under paragraphs 17(1) & 16(2) of Schedule 2 or of the Immigration Act 1971, or if you satisfy section 28A of the Act.

If you are not being questioned – and if you are white and middle class that is very likely - you can still help. You can record everything. You can inform people of their rights when they are stopped by officers. You can take people's contact details if they are stopped. If there is a case against them, a failure of protocol by the officer will be relevant. You can get a useful fact-sheet of your rights for printing out and handing to people here.

It might be possible to build a case that the spot-checks are contravening the Equality Act 2010, which outlaws racial profiling or officials engaging a person on the basis of their appearance, race, colour, ethnic origin or nationality. Shadow immigration minister Chris Bryant raised this very fear last night.

Anecdotal evidence suggests it could be the case. Kensal Rise resident Phil O’Shea told his local paper: "I thought the behaviour of the immigration officers was heavy-handed and frightening. They appeared to be stopping and questioning every non-white person, many of whom were clearly ordinary Kensal Green residents going to work.

Matt Kelcher wrote in the New Statesman: "They didn’t seem interested in me and I walked straight through, but the two Asian women who entered the station after me were stopped, taken to one side and questioned."

Record what is going on. Officers are not obliged to stop everyone to prove that they are not discriminating, but a sustained attempt to question only non-whites could possibly open the door to a legal challenge.

The actions of UKBA warrant a strong counter-response. These are not their streets. They are our streets. This country does not require its citizens to prove their right to exist. Officials must justify to you why they are stopping you, not the other way round. This is the definition of a free country.

The Home Office is encouraging the very worst human qualities: suspicion, division, resentment, the cold, hard indifference of the state. Labour did it. And now the Conservatives are doing it. They all do it in the end, in a callous bid to placate a public sentiment on immigration which only hardens with each mean-spirited PR exercise.

Do not let them bully you. If you see a spot check, make sure they encounter an educated, confident civilian population who will hold them to account.

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