Only 1 in 10 British children regularly play outdoors. The National Trust wanted to get kids out of their bedrooms, away from their computers, and into the outdoors. Encouraging families to spend time outside would be good for children (fresh air and exercise is so much healthier than i-pads and TV), but also good for the National Trust (who manage a vast network of countryside properties and estates).

Our mailing was part of a bigger campaign, ‘50 things to do before you’re 11 ¾’, to achieve this behaviour change.

Encouraging children to have adventures isn’t part of the British psyche. So we chose an activity that kids would find “awesome”, and the parents would be inspired by too - a night walk. We dramatised it a way that only direct mail could deliver. We sent the parents a poster, for their child’s bedroom wall. Not any poster, but a magic one. One, that if the child sneaks a peak at it in the middle of the night, it comes alive, just as nature does. We painstakingly created two scenes – a daytime scene, and a hidden night-time scene, with all the amazing animals that could be seen at midnight made out of phosphorescent ink. We tracked down the very same ink that the Highways Agency use to get things noticed at night, so that our night-time image would really stand out, and create genuine surprise.

The mailing drove overnight response: app downloads increased 11 times; social mentions doubled; site traffic and dwell time increased (from 2 to 7 minutes). The 90,000 children who signed up to the integrated ’50 things’ campaign spent a combined total of 23 years playing in the outside. The long-term effect on retention is too early to see, but increased engagement with the National Trust should have a healthy financial benefit too. The most important result was happy, healthier children, and happy parents making the most out of their membership. One Mum tweeted “Loving the glow in the dark poster… it’s been quite a talking point at bedtime”.