Detention decisions engage statutory interpretation, Equality Act duties and Article 5. In practice, challenges tend to succeed or fail on documents that already exist: screening records, medical notes, and the internal reasoning behind a decision to detain or to maintain detention.
Those documents are obtainable. A subject access request under Article 15 UK GDPR carries a one month deadline and costs nothing, and it will often produce material that would otherwise wait months for litigation.
We advise on what to ask for and how to ask for it, and on whether what comes back discloses a case worth taking further.