The bath bomb leaves a pretty trail of blue and yellow throughout the water. Keen fans will notice it's an update of an earlier design.
"This version is slightly different from the original Northern Lights bath bomb we had a couple of years ago. We decided to make the colour inserts visible from the outside and add two different bath bomb mixtures to create an entirely different effect in the bath. The purple mixture in this one fizzes slowly whereas the yellow is quicker, which helps to create the spiral effect you see in the bath."