A handful of multibillion-dollar deals have helped push mergers and acquisitions levels within the European Union to decade highs - but at least one lead adviser is cautious about celebrating the record levels of activity.

The Italian infrastructure company Atlantia's $35bn bid for Spain's Abertis and the French lens maker Essilor's $16bn deal for Luxottica have helped push M&A deal value within the European Union past $200bn at this point in the year for the first time since 2007, according to Thomson Reuters data.