Suddenly, they are everywhere: stretched across balconies, flapping from car antennas, and pinned to coat lapels the world over in a moving display of solidarity with the community that was brutally terrorised on Sunday after a bigoted assault at a gay nightclub in Orlando, Florida. At first glance, the rainbow flag’s joyous refraction of colour may seem a strangely sunny response to the dark savagery of the deadliest mass shooting in US history. But as we watch its jubilant stripes bind together communities around the globe, it is worth pausing to reflect on the origin of a cultural symbol that was propelled into iconic status nearly 40 years ago by heartbreaking tragedy.