In A Study in Stone, Alan tells Dan the password for his laptop.
It's: Hwggnimw1n
Dan guesses that the w1n stands for Windows and Alan admits this. Dan suggests that the rest is an acronym, and although Alan refuses to confirm or deny this, it might well be true.
Can you guess what the letters might stand for?
Pop your answers in the comments below. There's no prize except the honour of a job well done.
Have a go!