Put the flour and a dash of salt and pepper in a bowl, then crack in the egg. Slowly whisk in the milk or milk-and-water mixture until the batter is smooth and frothy.
Separate the sausages from each other. Stretch each rasher of bacon by laying it on a chopping board and running the flat edge of a knife along the rasher until it is half as long again. Wrap a rasher of bacon around each sausage.
Pour the oil into a roasting tin and add the bacon-wrapped sausages, keeping them spaced apart. Roast in a preheated oven, 220°C (425°F), Gas Mark 7, for 5 minutes until sizzling. Whisk the batter again.
Take the roasting tin out of the oven and quickly pour in the batter, making sure that the sausages are still spaced apart. Return the tin to the oven and cook for about 20 minutes until the batter is risen and golden and the sausages are cooked through. Delicious with baked beans and mashed potatoes.