Now Allen & Overy and Shearman & Sterling have completed the first-ever top-tier transatlantic merger, it is time for a few questions.

Behind the shiny communications façade, insiders will no doubt be wondering: can the A&O management really manage such a large U.S. operation from overseas? Was Shearman in such bad shape that the legacy U.K. firm is effectively catching a falling knife? Will the cultures gel?