Technology doesn't have to be high tech

The winner of the FT Climate Change Challenge is a solar powered cardboard oven. Two cardbaord boxes, one inside the other, with an acrylic lid. Estimated cost to make: £3.50.

Fantastic.

It reminds me of an invention during my high school years. It was called the wonder box. Simply a cardboard box lined with newspaper on the bottom, and cushions filled with polystyrene beads around the sides and top.

My Gran had one which she used to cook the potatoes for our family barbecue.

It worked like this: you would bring the pot of potatoes (or whatever) to the boil on the stove in the usual way. Then you would pop the pot into the box, tucking the cushions around it, and covering it with another. Then close the box and leave it. It always made perfect potatoes and you couldn't burn them, either!

Here is a slightly more sophisticated version.