The unprecedented pressure of working on the frontline during the Covid-19 pandemic had a demonstrable impact on the mental health and wellbeing of health and social care workers in the early stages of the pandemic, however, less research has focused on workers' experiences over the longer course of the pandemic. We set out to develop an explanatory model of the processes that helped and hindered the coping of HSCWs working over the course of the Covid-19 pandemic. Twenty HSCWs based in the UK took part in the study. They completed semi-structured interviews 12-18 months after the peak of the first wave in the UK. Interviews were transcribed and analysed using grounded theory methodology. The analysis identified eleven theoretical codes: personal context, organisational resources, organisational response, management, colleagues, decision-making and responsibilities, internal impacts, external impactors, safety, barriers to accessing support and temporal factors. The findings suggest that factors related to the individual themselves, their personal context, the organisation they work in, their managers, the support structures around them and their sense of safety impacted on HSCWs; ability to cope. Some factors changed over time throughout the first year of the pandemic, such as workload and staff illness, which further impacted HSCWs' coping. There were many barriers to accessing support that also impacted coping, including availability, awareness and time. The relationship between the factors that impacted coping are represented in an explanatory model. The findings extend previous studies on the mental health impact on frontline HSCWs working during Covid-19, providing novel insight by developing an explanatory model illustrating the underlying factors that impacted their coping experiences over the course of the pandemic in the UK. The findings from this study may assist in the development of improved and more effective support for HSCWs going forwards.