Spy Pen Spy Pen Spy Pen Spy Pen £3.25 Quantity: at £3.25 each Add To Basket This clever spy pen lets you write secret messages only revealed by the built in U.V. light! Perfect for any budding spy. Pen height: 13cm / 5 inches. Warning: Not suitable for children under 3 years of age as small parts may present a choking hazard.