weigh the brown rice into a smallish bowl and cover with boiling water at least an hour in advance - or overnight with cold water if you work that far in advance...... Soaking the brown rice overnight or in boiling water will give a better more even result.
weigh the pudding rice into the the large pyrex dish - and add the pre-soaked brown rice - to a dish 1.2 litre in size.
weigh in the two sugars directly into the dish.
add around 300g of the milk and stir well to disolve most of the sugar.
pour in the rest of the milk
grate or sprinkle the ground nutmeg & cinnamon
add the margarine in a few separate lumps
you can add the optional lemon zest now
place in a pre-heated oven at 150°C - you can put it on the floor of the oven and set the temp to 175°C non-fan and cook other things at the top of the oven that need a higher temperature at around 175°C
What you're aiming for is the rice to be fully cooked, but there to be plenty of nice liquid to surround the rice. It doesn't want to be sticky and too dry.