Witnessing the surprise departure last week of Norton Rose’s four-partner leveraged finance team to Allen & Overy (A&O), the casual observer would conclude that the cosy, no-poaching consensus between the City’s top firms was at last over.

A closer inspection, despite illustrating once again that A&O is that shade more aggressive than its magic circle rivals when it comes to expanding its core banking practice, reveals a slightly more ambiguous state of affairs.