Make cake batter according to directions on packet, divide mixture evenly between four greased 25cm x 8cm (10 inch x 3 inch) bar tins. Bake in moderate oven, 30 minutes, or until cooked when tested. Turn cakes on to wire rack to cool.

When cooled, cut bar cakes in half vertically to give eight equal pieces. Reserve five of these to make tops of the four carriages and back of engine.

Cut remaining three pieces in half horizontally to give six equal pieces, five of which form the bases of the engine and four carriages.

Cut off one quarter of remaining piece to add to engine base to extend it, discard remaining three quarters.

Cut a 4cm (1 ½ inch) wide slice from sponge roll, hold slice upright and cut out smoke stack shape with a 2.5cm (1 inch) plain cutter. Use the rest of the sponge roll for engine. Assemble cake, as shown, on prepared board.

Make Vienna cream: Beat butter until white and creamy. Slowly add half icing sugar, beating constantly. Continue beating and slowly add in milk, then remaining icing sugar. Mixture should be smooth and easy to spread with a spatula.

Divide Vienna cream into five equal portions, tint each portion with different food colouring. Cover tops and sides of engine and carriages each with different-coloured Vienna cream.

Join carriages with pairs of jube rings. To do so split one ring, push the other ring through it, press on to Vienna cream.

Outline engine and tops of carriages with thin licorice, as shown.

Cover top and sides of smoke stack with red Vienna cream, coat with chocolate sprinkles, position, as shown. With a skewer, make holes through five pieces of popcorn, thread on to pipe cleaner, insert into smokestack.

Place whole ice-block sticks across front, back and between carriages, as shown, to represent sleepers. To make other sleepers, break ice-block sticks into 4cm (1½ inch) lengths, slide them underneath edges of cake on both sides. Double strips of licorice on either side of train represent tracks.

Position chocolate biscuits, as shown, to represent wheels, stick round coloured chocolate buttons on chocolate biscuits with a little Vienna cream.

Cut a 4cm x 1cm (1½ inch x ½ inch) strip from wafer, press strip firmly on to bottom front of engine. Arrange pieces of 2.5cm (1 inch) licorice against wafer, as shown, to represent "cow catcher".

Pile popcorn on top of carriages, decorate rest of cake with coloured buttons.