AJ Gallagher

The $3.57bn side deal is contingent on the closing of the bigger merger, which itself needs approval from regulators including the European Commission and Department of Justice.

The business looks well placed to succeed if it can keep retention in check and reinvest to build broader capabilities.

S&P said it believed Gallagher can "non-disruptively absorb the acquired business".

AJ Gallagher has won the coveted AerCap account from Willis Towers Watson, Insurance Insider understands. AerCap is the biggest aircraft leasing company in the world.

The AJG CEO vowed to invest in Willis Re assets while stressing the quality and security of the team.

The buyer says the deal involves revenue of about $1.3bn and earnings of around $357mn.

The merger partners are working towards a third-quarter completion after a side-deal they say addresses EC concerns.

Aon and Willis have been in talks with AJ Gallagher over a sale of assets the broking houses must make to gain approval for their pending merger from antitrust regulators.

The report says a final decision on the structure of the deal has yet to be made.

The deal could be signed later this week or at the weekend, sources said.

The intermediary has been expanding its presence in the Australian market considerably since the acquisition of Wesfarmer’s insurance business for $933mn 2014.

With a sale of the remedy assets to AJG not yet agreed, the firms will have to choose their words carefully this week.