On a visit to friends of our who have two small boys, a squabble broke out over colouring pencils.

“Josh, you’ve got loads of pencils, give Jack one” said his Mum sternly

“No!” was the answer.

Mum bristled and was about to go into punishment mode. Jack was on my knee, so I tried a different tack.

“Which pencil can Jack use?”

Josh scanned the pencils in front of him, then held one up and said “This one.”

Our friends dubbed me ‘Supernanny’ – tongues firmly in cheek – but actually I was just trying out some of my green jujitsu style thinking. People like having a choice – if you give people a single option, they will automatically add an alternative – “no!”. If you give them more options then they tend to pick from those options, rather than considering others. So you simply make sure the options on offer are all environmentally preferable.

And better still you stack the choice towards the greenest option – making that choice the default or most convenient and your least green option the most difficult.