Grease a large loaf tin that will fit on the lower rack of the halogen oven. Line the bottom and long sides with a strip of greaseproof paper. Grease the paper.
Cream together the butter, sugar and vanilla using a hand-held electric whisk until light and fluffy. Gradually beat in the eggs. Sift the flour and baking powder into the bowl and stir in until just combined. Turn into the prepared tin and level the surface. Place on the lower rack of the halogen oven.
Set the temperature to 175°C (347°F) and cook for 25 minutes until risen and firm to the touch. Transfer to a wire rack to cool.
Hull the strawberries, halving any large ones, and mix with the other fruits. Lightly whip the cream. Melt the redcurrant jelly in a small saucepan with the measurement water until smooth. Split the cake in half horizontally and sandwich together with half the cream and fruits. Drizzle with half the redcurrant jelly. Position the top half of the cake and decorate with the remaining cream and fruit. Spoon over the remaining redcurrant jelly.