After the success of eradicating smallpox, the journey began nearly 40 years ago to also remove polio from the planet. The challenge of consigning a second disease to the history books is ongoing, with $1 billion per year being spent trying to destroy it. The simplest of all public health interventions - a few drops of vaccine into a child’s mouth-is enmeshed by a complex web of geopolitical barriers. The definitive interruption of poliovirus transmission will only be possible if the Polio Programme can overcome them.