Enid Blyton's children's book range has sold millions of copies and even now, 70 years after the first book was published, still sells 2 million copies a year. 

The front of the card reads "Five Go To Party Island" and features a rowing image in the iconic style of Enid Blyton's stories. The inside message says, "Wishing you a birthday adventure you'll never forget!" There is also lots of space to write your own personal message.