It turns out that it's Concatenate.
Here's a picture of what I had and what I wanted.
Obviously my first port of call was Twitter.
@JoBrodie make a third column and use concatenate, so basically C = concat(A,B) http://t.co/6MO2aDoZKj
— Lauren G (@geeoharee) October 14, 2014
@JoBrodie = A1 & " " & A2
— Spike (@tenbus_uk) October 14, 2014
I used the second suggestion and it worked, hooray.