Piraeus Bank, Greece’s fourth-largest lender, will go ahead with the acquisition of a 27 percent stake in smaller peer Proton after the completion of due diligence on Monday, it said yesterday. Earlier this week, Piraeus Bank announced it had agreed to acquire the stake in an all-share deal (one Piraeus share for 5.5 Proton Bank shares) with a view to merging with the smaller lender. Piraeus said the same share-swap offer will also apply for the remainder shareholders. Any changes to Proton Bank’s board of directors will be undertaken in cooperation with its current management in order to improve operations, Piraeus Bank added. Analysts said the deal is not seen as having a significant impact on Piraeus, valued at 3.6 billion euros, but will help with plans to expand its branch network.