Mr Dursley was the director of a firm called Grunnings, which made drills.  

He was a big, beefy man with hardly any neck, although he did have a very large moustache.

An even more sophisticated form of code is sometimes called a Vigenére code. In this, we use a table like the one below and a keyword. Combining the letter from the word to be coded with the letter of the keyword gives the letter to use in the code. Once the keyword is finished, we start again with its first letter.

Let’s try using the codeword peter to code the message victory at Poltava.

Now see if you can decode the following code, which was coded using the keyword: lemon

Aifse Ambse amoyro e bspv sr dvnoxsq aibdrc.

This code is quite difficult to break if you don’t know the keyword. In fact the coding method was published in 1553 and it wasn’t until 1863 that a general method was developed for breaking these codes (which isn’t super easy).

Now that you know various ways of encoding messages you will be able to encode messages for other students in the class. Start with some simple messages and start by telling them the code or the keyword you have used, then you can gradually make things harder by not telling them how you have encoded the message.