For the Panna Cotta, place the gelatine into a bowl of cold water to soak. Pour the milk into a small pan, split the vanilla pod and scrape out the seeds adding both pod and seeds to the pan. Bring the milk to the simmer and stir in 25g of the sugar ensyring the sugar is dissolved.
Measure 250ml of the cream into a large mixing bowl then strain the milk into the cream. Mix well, cover and refrigerate. The mixture must now be chilled until it begins to thicken, it can then be poured into lightly oiled moulds and refrigerated overnight ready to serve. If the mixture is not thickened before moulding, the vanilla seeds will all fall to the bottom of the mould and spoil the presentation.
Next make the caramel. Please wear rubber gloves for this as sugar can give a nasty burn and is almost impossible to remove if it drips onto the skin. Heat a medium (10") heavy-based frying pan and sift 375g of caster sugar into the centre of the pan to make a pyramid half the diameter of the pan. The heat will slowly start to melt the sugar. When the pyramid starts to collapse, give the pan a shake. When there is more liqued than dry sugar, use a heatproof spatula to work in the rest of the sugar and break down any lumps. When you think it's the perfect colour, keep on the heat and carefully begin to stir in the remaining cream. Be very careful as the frying pan will start to bubble and splutter the moment you add liquid. Add the cream in splashes of about 50ml. If you add too much at once, you'll get lumps of caramel. Too little and the mix may start to burn.
For the fruit, place the water, remaining caster sugar and lemon zest and juice in a pan and bring to the simmer. Reduce the syrup by half then thicken lightly with the arrowroot. Allow to cool. Once cooled toss the washed and halved fruit in a little of the sugar syrup. To serve, turn out the Panna Cotta onto a plate and gently pour the fruit and syrup gently around the Panna Cotta with caramel.