In the UK the government agency responsible for immigration and the border is the Home Office. If you enter the UK without papers or become undocumented through overstaying your visa, then almost the only way to status is through claiming asylum or establishing a “private and family life”. You do so by making an application to the Home Office. You can make both types of claim at any time, but, especially with asylum, the earlier you claim asylum the better. You can also make both types of claim at the same time.
The UK, like the rest of Europe, tries to make things difficult for asylum seekers and other undocumented people. In the UK this strategy is known as the “hostile environment” (recently the government tried to rebrand it the “compliant environment”).The good news is that it doesn’t work very well. Every city has self-organised migrant community groups, solidarity activists, NGOs and charities working to support people without papers and help people survive and thrive in the UK.
The Hostile Environment has two parts. The first is to deny you access to basic necessities — like money, housing and healthcare — to encourage you to leave “voluntarily”. The second part is to turn everybody into a border guard. If you are going to get the job, rent a house, open a bank account, see a doctor in hospital, or have any interaction with the police or local government, then it is expected that the person you are interacting with will check your papers. You can find out more about the hostile environment here: http://www.libertyhumanrights.org.uk/wp-content/uploads/2020/02/Hostile-Environment-Guide-%E2%80%93-update-May-2019_0.pdf
In theory, without the right papers, you can’t work, rent a house or access the same support that unemployed citizens receive. It is important to note that even though you will be said to have No Recourse to Public Funds (NRPF), you can sometimes get different forms of state support, even getting money each week. Healthcare is a topic in its own right, but you are always entitled to free accident and emergency treatment (A&E) and free primary healthcare – visiting a General Practitioner (GP). You should be able to register with a GP or attend A&E without papers. Especially in England, as opposed to Scotland, Wales and Northern Ireland, many other types of healthcare are not free and will involve having your papers checked.
If you don’t have papers or you have obviously false papers, then the person or the authority checking them might report you to the Home Office. The police will almost always report you to the Home Office. If the Local Authority offers you support, then they have to report you to the Home Office. If you owe a hospital more than £500, then they will also inform the Home Office about you. Businesses and landlords may or may not report you to immigration.
The Hostile Environment is enforced by the threat of immigration detention. The UK can lock you up if they think that you have no right to be in the UK. There is no time limit on detention, but, in theory, they can only hold you to make it easier to remove you from the country. You can get released by applying for immigration bail. If you can persuade the Home Office or an immigration judge that there is no realistic prospect of removing you, that you are not going to go underground and that you are no threat to other people in the UK, then you will be granted Immigration bail and released from detention. In general, if you have an application in with the Home Office, then there is no realistic prospect of removing you and it is very hard for the authorities to keep you in detention. You can get more information about applying for immigration bail here: https://www.biduk.org/pages/6-information-for-detainees
If the Home Office know that you are in the UK and you do not have leave, then, in general, they will ask you to report at regular intervals to one of their offices. This is known as signing. Most people who go into detention are taken into detention when they go to sign. If you are signing regularly, you cannot be accused of trying to avoid immigration control. This can be helpful when it comes to making an application for leave based on your Private and Family life or a bail application from detention.
You might also end up in detention if you have to interact with the police. Even if you are just a witness to a crime, they can check your papers, hold you and detain you. Sometimes a special unit of the Home Office, immigration enforcement, do an immigration raid at a workplace or at your house. Immigration Enforcement officers do not have very many powers. In particular they cannot enter without permission unless they have a warrant or a letter from an assistant director in immigration enforcement. Normally you do not have to let them in. They can try to stop you on the street, but you don’t have to answer their questions. Unfortunately, they can arrest you if they have reasonable suspicion that you have broken immigration laws. If they do arrest you, you will be taken into immigration detention. You can find more information about immigration raids here: https://antiraids.net/
Despite all the effort put in by the Home Office, they are not very effective. Between March 2018 and March 2019 they only managed to force 8,637 people out of the country. A further 13,738 people agreed to give up and go back. https://www.gov.uk/government/publications/immigration-statistics-year-ending-march-2019/how-many-people-are-detained-or-returned. There are no accurate figures about the number of people without leave in the UK. It is safe to say that there are well over half a million undocumented people. Even including the people who “agreed to go home”, they got less than 0.5% of the people they were targeting. They are not even very good at getting detained people out of the country. About 60% of people who are taken into immigration detention are released back to the community.
The major problem with the hostile environment is not that it will stop you being in the UK, it is that it is soul destroying. The best way to combat the hostile environment is to get organised. If you can find or form a group of people without papers, then you can support each other to understand your rights. The hostile environment works by excluding people from society. Self organised solidarity groups and other antiracist formations work to bring people in. There is a large and growing movement against the UK border regime. Do not be scared to speak up. People will support you and you will win.