Preheat the oven to 150C/300F/Gas 2. Grease a 20cm/8in deep round cake tin and then line the base and sides with baking parchment.
Cut the cherries into quarters, put in a sieve and rinse under running water. Drain well and then dry thoroughly on kitchen paper.
Beat the butter and sugar together in a large bowl until light and creamy. Beat in the eggs, one at a time, to prevent them from curdling. Sift in the flour and mix it in a little at a time. Stir the fruit, peel, zest and mixed spice thoroughly into the mixture. Place half the mixture into the prepared tin and level the surface.
Take one-third of the marzipan and roll it out to a circle the size of the tin and then place the circle on top of the cake mixture. Spoon the remaining cake mixture on top and level the surface.
Bake in the preheated oven for about 2½ hours until well-risen, evenly brown and firm to the touch. Cover with foil after one hour if the top is browning too quickly. Leave to cool in the tin for 10 minutes and then turn out, peel off the parchment and finish cooling on a wire rack.
When the cake is cool, warm the apricot jam in a small saucepan. Brush the top of the cake with a little of the jam and roll out half of the remaining marzipan to fit the top of the cake. Press firmly on the top and crimp the edges to decorate. Mark a criss-cross pattern on the marzipan with a sharp knife. Form the remaining marzipan into 11 balls.
Brush the marzipan with beaten egg and arrange the marzipan balls around the edge of the cake. Brush the tops of the balls with beaten egg, too, and then place the cake under a hot grill to turn the marzipan golden-brown.
To crystallise the primroses, whisk the egg white in a bowl until frothy. Snip the long stalks off the primroses, then, using a paint brush, carefully paint the petals of each primrose with a little frothy egg white, then turn the flower over and paint the underside of the petals and the little stalk.
Cover the flowers in caster sugar until all the egg white is evenly coated, and leave to dry completely. You can either just lie them carefully on non-stick parchment, or, to help keep the flowers’ shape, you can stretch non-stick paper over a plastic box or bowl, securing it in place with string or a rubber band, and then pierce several holes in the paper using a skewer. Place the stems of the crystallised flowers through the holes, allowing the paper to hold and support the flowers in a more natural position as they dry and harden. You will need to make the crystallised flowers at least a day in advance.
Decorate the cake by arranging the crystallised primroses on top and tying a ribbon around the middle.