India, May 7 -- For decades, at exactly 9.00am, a mechanical wail would ripple through Mumbai's neighbourhoods. It wasn't an emergency. It was routine.

The city's air raid sirens - mounted on rooftops of police stations, government offices, railway buildings and municipal infrastructure - were a holdover from a more anxious time. After the 1971 war, these daily tests became a civic ritual. Office-goers, schoolchildren, shopkeepers all knew the drill. The siren marked the start of the working day. People set their watches to it.

And then, one day, it stopped. No warning. No replacement. The sound simply vanished from the city's busy life, and little did anyone notice in the new era of digital watches and cell phones.

Today, as the count...