Preheat the oven to 200 degrees C and lightly butter an 8-inch springform cake tin.
Melt the butter and pour into the crushed biscuits. Mix well, press down evenly in the cake tin to make a base and bake for 10 minutes. Remove from the oven and cool while you make the filling. Then lower the temperature to 150 degrees C.
To make the filling, blend the 3 bananas and lemon juice in a food processor until smooth.
Pour it into a large bowl and mix it well with the other ingredients for the filling. Use a hand mixer to remove any lumps. Pour filling over the biscuit base and bake in the centre of the oven for 1 hour. When the middle of the cheesecake is only slightly wobbly, turn off the oven and leave the cheesecake inside to cool slowly until completely cold.
For the sauce, heat butter, sugars and syrup in a saucepan over a very low heat, till dissolved completely. Cook for 5 minutes, add the cream and cinnamon powder and stir until everything is smooth. Remove and cool completely before pouring it into a jug for serving.
When the cheesecake has cooled, toss the sliced bananas with the lemon juice in a bowl. Gently spoon some sauce on the cake and layer the bananas in overlapping circles all round it. Serve rest of the sauce separately.