Sompo Holdings has completed its acquisition of Bermudian-based Aspen Insurance Holdings Ltd, bringing the island reinsurer fully under the Japanese group’s control and ending its run as a publicly-traded company.

In August, Sompo announced it would pay $3.5 billion for the company headed by Mark Cloutier, adding $4.6 billion in gross written premium to Sompo’s balance sheets.

The Tokyo-listed insurer announced on Tuesday that a wholly-owned subsidiary of Sompo International Holdings Ltd purchased 100 per cent of Aspen’s issued Class A ordinary shares. Aspen’s Class A shares, which traded under the symbol AHL, have ceased trading on the New York Stock Exchange.

Aspen’s preference shares will remain listed on the NYSE, with their existing rights and terms unchanged. Sompo said it may, from time to time, seek to redeem, repurchase or delist those securities.

The transaction strengthens Sompo’s global property and casualty platform and expands its reinsurance footprint from Bermuda, according to the company.

Mikio Okumura, Sompo Group chief executive, said: “Today marks an important milestone in our strategy to continue Sompo’s plans for profitable growth, to deploy capital strategically and to ensure a globally diversified property and casualty platform. I am pleased to welcome the Aspen team to Sompo.”

James Shea, CEO of Sompo P&C, said the deal showed the group’s commitment to growing through market cycles.

“The addition of Aspen’s reinsurance and insurance portfolios along with a more substantial presence in the United Kingdom enable us to accelerate our commitments to our customers, people and shareholders,” Mr Shea said. “Aspen’s culture of underwriting and customer focus will ensure a smooth transition as we engage as one organisation with our customers and partners.”

Aspen will transition to trading under the Sompo brand. Mr Cloutier, Aspen’s executive chairman and group CEO, will move into an advisory role with Sompo.