Around 28,000 people are detained indefinitely by the Home Office each year ostensibly for the purpose of facilitating their removal from the UK under Immigration Act powers. Most are detained for a few weeks, but many are detained for months, even years, with no prospect of release. Around 500 are detained in prison after their sentence has been served. The remainder are in nine Immigration Removal Centres (detention centres) or three Short Term Holding Facilities, which are prisons in all but name. At the end of 2016, there were 2738 people in detention of whom most were men. In 2016, 53% of those released were released back into the community, their detention having served no purpose. 

There is at least one visitors' group attached to each detention centre, and short term holding facility, and all are members of AVID. Those who are detained become very vulnerable because of the disorientation, disempowering and dehumanising effects of not knowing when or if they will be released. Among them are people who have been tortured and/or suffered imprisonment in their home countries from which they have fled for safety. The UK is the only country in Europe which does not have a time limit on detention. 

Isolation and anxiety are high among those detained, who are frequently held at a distance from family, friends and support networks. It is now widely understood that detention without time limit causes mental ill health, and can exacerbate pre existing conditions. Many suffer from some form of mental illness which is only exacerbated by detention.  A friendly face who visits for the sole reason of offering emotional support and practical advice can make an enormous difference to their well-being and is often described as a 'lifeline'. AVID's constituent visitors groups have around 600 volunteers among them who visit their particular detention centre - their impact is huge, relieving loneliness by just being a listening ear. AVID works to set up new groups, to support existing groups, to provide a collective policy voice for change, and to raise awareness of the realities of detention nationally.