It will be a long night. At Quinta dos Murças’s Lagares winery, the lagares (tanks) are all filled and the grapes are trodden, the old-fashioned way, as they have been in the Douro for centuries. The group, standing in a line, arms over each other’s shoulders, crush the grapes as they sing traditional songs of the region. There’s a festive atmosphere but the work is done with great rigour.