David Haig’s play Pressure looks at the Scottish meteorologist, James Stagg, who advised Eisenhower about the weather in the week before D-Day. The play works by detaching us from our foreknowledge of events. We’re aware that the landings went off smoothly on 6 June in fine conditions. However, D-Day was originally scheduled for 5 June, and for the preceding month southern England had basked in a prolonged sunny spell.