Arthur J. Gallagher has completed its $US3.25 billion ($4.5 billion) acquisition of Willis Towers Watson (WTW) treaty reinsurance brokerage operations after reviving a deal flagged before the collapse of Aon’s proposed takeover of WTW.

The combined businesses will trade as Gallagher Re from more than 70 offices across 31 countries and incorporate about 2400 personnel.

“I am confident the combination will deliver tremendous value to our clients, our global brokerage and risk management teams and our shareholders,” Gallagher Chairman, President and CEO Patrick Gallagher said.

The company says the acquisition brings specialist expertise, underpinned by analytics capabilities including catastrophe modelling, dynamic financial analysis, rating agency analysis and capital modelling, that will provide value to insurance carriers and capital providers.

Gallagher Re will be led by James Kent, Global Reinsurance CEO, who will report to Gallagher Global Property & Casualty Brokerage CEO Tom Gallagher.

“We are bringing together highly complementary and well-respected reinsurance businesses to create a truly compelling unified reinsurance platform,” Mr Kent said.

Aon and WTW said in May that they planned to sell the Willis Re reinsurance business and certain UK, European and North American operations to Gallagher as part of efforts to win regulatory clearance for their merger.

The deal to create the biggest insurance brokerage in the world was called off in July after Aon reached an impasse with the US Department of Justice, also throwing the Gallagher deal into doubt.

But in August Gallagher said it would still go ahead with the treaty business acquisition and told the market the deal was expected to close in the fourth quarter of this year subject to regulatory approvals.