For the strawberry jam, heat a small frying pan until hot, then add the strawberries and cook for one minute. Add the sugar and lemon zest and juice and cook for 3-4 minutes until the sugar has dissolved and the mixture has thickened slightly.
Remove half of the mixture from the pan, place into a blender and blend to a purée.
Return the purée to the pan with the remaining cooked strawberries, mix well and cook for a further 3-5 minutes until thick. Remove from the heat and cool.
Place the flour, sugar and suet into a bowl and mix thoroughly.
Make a well in the centre of the mixture then gradually add enough water to make a soft dough. Knead lightly until smooth.
Turn onto a floured surface and roll out to an oblong about 1cm/½in thick. Spread the jam out on the pastry leaving a 2.5cm/1in border.
Roll up from the long side into a pinwheel. Place the roly-poly into a loaf tin and cover with aluminium foil, sealing tightly.
Place a plate into the bottom of a large pan of water, place the loaf tin on top and fill the pan two-thirds full of water (do not allow the water to reach the top of the tin) and bring to the boil. Cover, reduce the heat and steam for one hour. While the roly-poly is steaming, preheat the oven to 200C/390F/Gas 6.
Remove the pudding from the tin and place on a baking tray in the preheated oven. Bake for 15 minutes, or until browned.
For the custard, place the egg yolks and sugar in a bowl and whisk until well blended.
Combine the milk, cream and vanilla pod in a saucepan and bring to the boil. Immediately reduce the heat and simmer for one minute.
Pour the milk onto the egg mixture and whisk in. Return the mixture to the saucepan and heat slowly, until the custard has thickened enough to coat the back of the spoon. Remove and discard the vanilla pod.
To serve, cut the roly-poly into thick slices and serve with the custard and any extra jam.