Place the flour in a large bowl. Sprinkle over the sugar and salt and mix in. Sprinkle over the yeast. With your hands, mix in the water and the oil.
Turn onto a floured board and knead for about 10 minutes. Oil the bowl and then pop the dough back in. Cover with a damp tea-towel and leave in a warm place for 90 minutes until doubled in size.
After this time, knock the dough back (knocking the air out) and knead again for 5 minutes. Shape the dough into small balls and then place on a tray lined with baking parchment in a warm place to prove for another 20 minutes.
Heat enough oil to fill a deep saucepan half full. When the oil is hot enough (test by gently dropping a bread crust into the oil. If it bubbles and browns, then the oil is hot enough). Using a slotted spoon, gently drop two balls of dough at a time into the oil.
They take about 3-4 minutes to cook. Turn them once to make sure both sides are golden brown. Remove and place on some kitchen paper to soak up the oil. Now toss in lots of caster sugar. Repeat with all the balls of dough.
Fill a piping bag (with a round nozzle) with the jam and poke the nozzle into each doughnut and squeeze in some jam. Finally, sprinkle with the glitter and devour.