This report explores the concept of market supply and demand, focusing on the falling petrol and diesel prices in the UK during the Covid-19 lockdown. It discusses the factors that affect shifts in the demand and supply curves in the short and long run, as well as the long run elasticities of substitutes. The study concludes that equilibrium occurs when quantity supplied equals quantity demanded, and predicts that fuel prices will gradually rise as the impact of the virus slows down.