Aon PLC’s proposed acquisition of Willis Towers Watson PLC will create the world’s largest insurance brokerage, outstripping rival Marsh & McLennan Cos. Inc.

The deal announced Monday came a couple of days after the end of a standstill agreement between No. 2 ranked Aon and No. 3 ranked Willis Towers Watson that regulators required after the two firms ended possible merger discussions in March of last year.

The current proposal, which is expected to be completed in the first half of 2021, will still need to meet numerous regulatory requirements.

While analysts saw several advantages for Aon arising from the deal the merger of two of the three recognized global brokers will give risk managers fewer options when selecting their key service providers.

Under the terms of the deal, Willis Towers Watson shareholders will receive 1.08 Aon ordinary shares for each Willis Towers Watson share, according to an Aon statement announcing the deal. Based on Friday’s close, that would value the deal at about $29.86 billion. The share price of both firms fell sharply on Monday amid a broad market sell-off linked to falling oil prices and concerns over the coronavirus.

On closing, existing Aon shareholders will own approximately 63% of the combined firm, which will trade under the Aon name, and Willis Towers Watson shareholders will own approximately 37%.

The merged entity’s operating headquarters will be London. The firm “will be led” by Greg Case, CEO of Aon, and Christa Davies, chief financial officer of Aon, according to the statement. John Haley, CEO of Willis Towers Watson, who was due to retire at year-end, will be executive chairman.

Aon expects the deal will result in annual cost savings of $800 million by the third full year after the combination. About 73% of the savings will come from consolidation of the businesses and 27% from consolidation of infrastructure, the statement said.

The two firms currently compete in numerous areas, including retail broking, reinsurance broking and employee benefits consulting.

If the deal is called off due to antitrust concerns, Aon would pay Willis Towers Watson $1 billion, according to the terms of the offer.

The announcement comes less than a year after Marsh & McLennan completed its purchase of Jardine Lloyd Thompson Group PLC, which significantly extended its lead over Aon as the world’s largest brokerage. According to the three firms’ 2019 results announcements, Marsh & McLennan reported total revenue of $16.65 billion, Aon reported total revenue of $11 billion and Willis Towers Watson reported $9 billion.

Aon and Willis Towers Watson have also gone through significant transitions over the past few years.

In December, Aon completed a restructuring plan that saw 5,832 jobs eliminated following the 2017 sale of its outsourcing business. And late last month, the brokerage announced that Michael O’Connor, former co-president of the firm, would be leaving, which was the most high-profile of several executive departures over the past year.

Willis Towers Watson completed the integration of its two major legacy companies – brokerage Willis Group Holdings PLC and consultant Towers Watson & Co. – in 2018. And last month, Willis Towers Watson announced it was reviewing strategic options for London-based wholesale broker Miller Insurance Services LLP, which it bought in 2015.

Aon and Willis Towers Watson had preliminary discussions about a possible deal a year ago but called off the negotiations after news of the talks leaked.

The latest deal marks three decades of massive consolidation in the insurance brokerage business, as indicated by Business Insurance’s 1990 ranking of the world’s largest brokerages. If the Willis Towers Watson deal closes, Aon, which then traded as Rollins Burdick Hunter Group, will own five of the 1990 top 10 or their successor companies – Alexander & Alexander Services Inc., Corroon & Black Corp., Willis Faber PLC, Frank B. Hall & Co. Inc. and Minet Holdings PLC. Marsh & McLennan now owns the remaining three former rivals – Sedgwick Group PLC, Johnson & Higgins and Jardine Insurance Brokers Group.

Arthur J. Gallagher & Co. Inc., which has implemented its own widescale M&A strategy and currently would be ranked No. 3 on completion of the Aon/Willis deal, was ranked 12th in 1990.