You'll need a tube map - they're free from all tube stations. Fold it flat first.
Then, cut it half - it'll give you a perfect square of tube!
Fold the section with the map on in half, and crease firmly. You don't need the other half (although, you could use it for practise, or backup.)
Unfold the map, and turn it over. Then, fold each corner into the center. The creases you made in the previous step will show you the exact center.
Once you've done that, you'll have a small square of map like this. Make sure to keep the creases neat!
Fold half of the map lengthways into the center...
...and then the other half. You'll end up with a thin rectangle.
Then, fold the bottom and top into the center. You should be left with a little square. These are the toughest folds to make.
Now, an easy step! Unfold back to step 5.
Unfold the top and bottom triangles.
This next step is where the bit of paper transforms into a box! By tucking the sides up, and making two little triangles, the rest should all fall into place. Take a look at the picture if you're struggling!
Then, fold the triangle down to complete half of the box.
Repeat the last two steps on the other half of the map and you're done!