Background: Coronavirus Disease 2019 (COVID-19) is a pandemic of significant international concern, requiring decisive government actions with public understanding and subsequent adherence to control the spread. This study investigated the predictions of the public and healthcare workers (HCWs) at an early stage of the United Kingdom (UK) pandemic to assess their understanding of this novel virus and provide a reflection of the information readily available to them at the time. Method: A cross-sectional survey between the 18th and 20th March 2020 of UK adults was conducted via an anonymous 17-question online questionnaire using a snowball sampling technique. Simple descriptive statistics, repeated measures analysis of variance (ANOVA), and unpaired Mann-Whitney t-tests investigated significance at the P<•05 levels. Results: A total of 823 UK residents responded, of which 12•0% (n=99) were HCWs (doctors and nurses). The primary information sources used by our participants were BBC News, group messaging such as WhatsApp, and NHS England. The majority (38•9%) estimated government-enacted social restrictions would last two to four weeks. Mean best guess of total UK COVID-19 mortality was 1000 to 10,000 deaths, and the majority of participants (77•9%) revealed that they expected their day-today lives to be affected for less than six months in total. HCWs consistently estimated greater duration, scale, and impact of COVID-19 than nonhealthcare workers (Non-HCWs). Conclusion: Survey respondents greatly underestimated the duration and impact of COVID-19 on their personal and public lives. Non-HCWs made greater underestimates than HCWs. This provides a historical reference and highlights a lack of clear information regarding the pandemic at the time of the survey. There is an ongoing need for effective, realistic, and timely communication between government, front-line clinicians, and the general public to manage expectations of the course of the pandemic and, consequently, increase adherence to public health measures.