Methodology: A single blind randomised controlled trial evaluating the effectiveness, efficacy, and acceptability of sending a text message appointment reminder to prevalent women (women aged 47-53 years) living in the London Borough of Hillingdon 48 hours prior to their first breast screening appointment. 2,239 women without a history of breast screening, implant, or bilateral mastectomy were included in the study and randomly assigned in a 1:1 ratio to either the control group (n= 1,118) or the intervention group (n= 1,121). Women in the control group were invited to screening but received no reminder for their appointment, whilst women in the intervention group received a text message reminder 48 hours in advance. All women received an information letter about the study with their invitation from the West of London Breast Screening Service, which included a patient "opt-out" request form. Patients were not told whether they would be receiving a text message reminder or not. iPlato Patient Care Messaging was used to deliver the text-message reminders.