For the door, cut out a white rectangle from the sugar icing that is just short of half way up the cake. Add a blue window and a small ball for a door knob. Use piped royal icing to decorate the age of the birthday recipient in the window. To make the rubber ring, roll out a white sausage of icing and add four very thinly rolled strips of red icing at even intervals. Roll so that they are perfectly smooth. It should be no longer than 15cm, cut to size and position in a circle. Dampen and add to the top of the beach hut's roof.