The time kids spend outdoors gets smaller every day – but it’s hard to understand how much time is too little unless we can put it into a context that’s easily recognised.

The rights of prison inmates to outdoor time are laid down by the UN. This is not the case for children, who now spend less free time outdoors each day than prisoners.

The creative idea was to compare the time the average child spends outdoors with that of a prison inmate.

To bring this to life, we visited a high security prison in Indiana to film inmates, and ask them what their outdoor time each day meant to them. We then revealed that kids spend less time outdoors each day than they do, and we filmed their reactions. Because they truly understand what it means to have free time outside, they were shocked by this statistic.

The aim of the campaign was to maximise impact and get this issue onto the public's agenda. We therefore chose to go for a big, PR-led burst campaign, which launched in the UK and Brazil simultaneously.

We teed up the media with several PR-placed articles highlighting the lack of outdoor play and the announcement of Ken Robinson as our Dirt is Good Child Development Advisory Board Chairman.

With the media primed, 4th April was then our big launch. The primary focus was online, with the online film and related content taking over Twitter Moments (a Unilever first), a live Periscope broadcast by Sir Ken, and rich banners. Offline, the film was pushed out in cinema and custom-made 'prisoner kits' were mailed out to key influencers.

'Free the Kids' is the first phase ('Provoke') of a three-part campaign that encompasses Provoke, Educate and Facilitate.

In the first 3 weeks of the launch it got an impressive uptake by the media, with over 471 Million media impressions and 115 articles in renowned titles including Fast Company, Globo, CNN, The Times, the Guardian, The Telegraph and El Pais. As the objective of this campaign was specifically to get the issue of children's outdoor play onto the public agenda, this is an especially relevant measure of success.

There has also been significant engagement online, with thousands of mentions on Twitter on launch day alone, including retweets by influential bodies such as Greenpeace and Public Health.