In England and Wales, “child custody” is usually dealt with as child arrangements, covering where a child lives and time spent with each parent. Look for a London family solicitor with relevant experience, clear fees and availability, and check whether they are regulated by the Solicitors Regulation Authority (SRA). Ask about negotiation, mediation and court proceedings, as the best approach depends on the circumstances and the child’s welfare. You can also check GOV.UK for information about legal aid and family court applications.