Overview: Andrew Graham-Dixon looks at how the seemingly peaceful countries of Holland and Belgium - famous for their tulips and windmills, mussels and chips - were in fact forged in a crucible of conflict and division. He examines how a period of economic boom driven for the first time by a burgeoning and secular middle class led to the Dutch golden age of the 17th century, creating not only the concept of oil painting itself, but the master painters Rembrandt and Vermeer combining art and commerce together as we would recognise it today.