The year 1976 rises like a spectre whenever the sun shines for more than a few days. That long, dry, hot summer has become a regular reference point for people in their late forties and over searching for happy memories of childhood or young adulthood. Those too young to remember it will nevertheless be familiar with photographs of people dipping in the fountains in Trafalgar Square, walking alongside dried-up reservoirs or showing a ‘Blitz spirit’ as they filled buckets from standpipes in the streets.