BNY Mellon has seized the opportunity to buy the half share of German fund manager WestLB Mellon Asset Management that it does not already own, as part of a revamp of its asset management businesses.

The custody bank is not revealing the price it is paying for the manager, which looks after €25.5bn in assets. But investment bankers said it was unlikely to be high: "It's a perfectly sensible deal for both sides. I'm only surprised it's taken so long," one said.