Royal Dutch Shell was upgraded to buy from hold at ABN Amro, with the broker arguing it would fit with an investor looking to get share price exposure to a possible mega-merger. "We estimate the probability-weighted value of merger scenarios to be highest in its case, at up to 8% of the group's current market capitalization on the basis of cost savings and up to 18% if we include all potential sources of value creation from a merger," the broker said.