If you've read My Granny Writes Erotica then you will no doubt be familiar with the infamous 'My Ickle Pony Tail'.

Our prudish protagonist, Betty, receives one in the post. It has long, rainbow hair, a 'handle' with a tapered end and plays the tune of 'Ride a Cock Horse' in a high pitched tinny squeak. Betty struggles to work out what it's for. Guesses involve a garish hair decoration and a tickling device. Those of you who've read the book will know that it's for something else entirely.

But i...