Will any top level Volkswagen executives ever go to prison, as happened to a couple of sacrificial lambs thrown early on to US prosecutors? It's a question which comes to mind following the unexpected revelation last night that the US Justice Department has filed criminal charges against former VW CEO Martin Winterkorn, accusing him of conspiring to cover up diesel emissions cheating. Filing charges is one thing - getting the good Herr Winterkorn across the Atlantic to a US court room is the tricky bit.