The COVID-19 pandemic has necessitated physical distancing which is expected to continue in some form for the foreseeable future. Physical distancing policies have increased reliance on digital forms of social connection and there are widespread concerns about social isolation and mental health in this context. This qualitative study sought to understand how loneliness was experienced during physical distancing in the initial national UK COVID-19 lockdown. Eight individuals who reported feeling lonely during the initial lockdown were interviewed in May 2020. Interviews were analysed using reflexive thematic analysis. Four main themes were identified: (1) Loss of in-person interaction causing loneliness, (2) Constrained freedom, (3) Challenging emotions, and (4) Coping with loneliness. The loss of in-person interaction contributed to feelings of loneliness and digital interaction was viewed as an insufficient alternative. Social freedom could be constrained by distancing policies and by social contacts, contributing to strained personal relationships and feelings of frustration as part of loneliness. Fluctuations in mood and difficult emotions were experienced alongside loneliness, and distraction and seeking reconnection were commonly reported methods of coping, although they were less accessible. These findings indicate that physical distancing measures can impact loneliness due to the limitations they impose on in-person social contact and the perceived insufficiency of digital contact as a substitute.