This question is very complicated. In short, I would say that the first lockdown did not impact much economic performance, but the absence of fiscal support would have had terrible consequences on the UK GDP. Let me split this answer into three subparts. First, a fraction of the UK GDP is composed of exports. Given the unfavorable world economic conditions and the disruption of the global supply chain, this fraction would collapse independently of the lockdown. Second, lockdown prevented agents from consuming certain types of goods, the so-called non-tradable goods, like restaurants, pubs, hairdressers, and estheticians. So, how much would the households consume these types of goods in the middle of a terrible pandemic with a lot of uncertainty and full Intensive Care Units in the absence of the lockdown? My answer would be not much. Most likely, some households with low-risk aversion would keep going out, but the vast majority would cut this consumption type. In my opinion, the main difference between Sweden and the UK's economic performance lies in the severity of the pandemic more than the severity of the lockdown. Indeed, despite the high death rate, Intensive Care Units were never running at full capacity in Sweden. The high death rate's main reason was the high spread of the virus in care homes. Therefore, a considerable fraction of Swedish households kept consuming non-tradable goods during the pandemic. Third, I think that the absence of fiscal stimulus would have a terrible impact on the GDP. Indeed, the drop in export, the disruption of the global supply chain, and the aggregate demand decline would have led to a disproportionate default of UK firms and a large fraction of unemployment with catastrophic consequences for the UK GDP.