Chop the onion and bacon into smallish pieces (doesn't matter how small).
Add them to a frying pan and start to cook them.
After a few minutes, add the red wine to the pan and allow it to simmer to let the wine reduce.
Meanwhile, start to cook the sausages in the oven. I've used thinner sausages here, but you could easily use large thick sausages instead. The oven should be around 180 degrees centigrade.
After approx 5 minutes of the wine reducing, add the beans, mixed beans, chopped tomatoes and mustard into the pan. You can also add the sugar, but this is optional and some may prefer not adding it.
Let the ingredients simmer for approx 15-20 mins, stirring occasionally.
Place all the sauce and sausages in an oven dish and place in the oven for 30 - 40 minutes at 180 degrees Centigrade.
Serve with fresh chunky bread, tossed in a little olive oil and salt/herbs.