America's investment banking powerhouses are poised to take a commanding lead into the second half of the year in European M&A, after activity in the first six months of 2015 was driven by record US acquisitions of European companies.

At the six-month stage of the year, Morgan Stanley tops the European M&A advisory charts for the second year in a row, having worked on $218.9 billion of deals, according to preliminary data from Dealogic published on Wednesday.