Heat the oven to 160C/fan 140C/gas 3. Line a 2lb/900g loaf tin with a strip of baking paper, leaving the edges overhanging.
Brew the tea then drop in the dates and sultanas while still hot. Gently heat the malt extract and sugar in a small pan, stirring, until the sugar has dissolved. Cool until just-warm.
Put the flour, baking powder and a pinch of salt in a bowl. Mix in the melted sugar, bananas, fruit and tea. Tip the batter into the tin and bake for 1 hour.
Brush the top of the cake with more malt extract, then leave to cool in the tin completely. Wrap in baking paper then foil and keep for 2-3 days to mature and develop maximum stickiness before serving. Eat within a week.