So.... in addition to what we've done already. The full amount of berries was added on 14th September, nine days ago. According to the recipe, we've overdone the amount of time that the berries need to stand in the sugar and yeast. Also, we failed to add more than 4kg of sugar at that time.
Despite this, the fermentation was still carrying on today when we opened the barrel, as evidenced by the bubbling of the water escape trap at the top of the barrel.
Tonight, we strained off the fruit, separating from the icor (burgundy-red juice) with a coarse muslin bag. We transferred the liquid from one 60l barrel to another, newly sterilised with Campden tablets, using a jug and the muslin as shown in the photo above. We squeezed out the fruit as much as possible to extract every ounce of juice remaining in the fruit. By the end of the process of washing the fruit through with more water, and squeezing it out, we ended up with the sixty litre barrel full of purple-coloured proto-wine. Assuming that fermentation will continue, we have also added a further 7 kg of sugar, bringing the total to 11kg - which should hopefully result in a dry red wine which is drinkable.
The next stage will occur 4-6 weeks from now, at around the end of October, when we'll rack off the sediment - strain the wine through muslin again - at which point the primary fermentation ought to have ceased. Until then, the barrel is back into a warm outhouse with a water escape airlock on top to release the gas produced by the action of the yeast and sugar.