The Apollo moon programme has been called the last optimistic act of the twentieth century: over an intensive three-year period between 1969 and 1972, twelve men made the longest and most incredible of journeys. All were indelibly marked by it.

Of the astronauts who walked on the moon, only nine are still alive. One day in the near future there will be none; soon no-one on earth will have known the unique feeling of gazing back at us from another world.

The thought shocked Andrew Smith, a journalist who grew up in America during the moon landings, and he set out to find and interview the remaining moonwalkers to find out how the experience changed them.

'Where do you go after you've been to the moon?' In addition to this question that would prove hugely troubling to many of the returned astronauts, they also had to deal with being true celebrities. The walkers would forever be caught between the gravitational pull of the moon and the earth's collective dreaming.