Zurich Insurance Group AG's U.K. arm agreed to cover more than £2 billion of pension liabilities for the U.K. National Grid Electricity Group of the Electricity Supply Pension Scheme.

The transaction protects National Grid PLC, which operates the U.K.'s electricity infrastructure, against the risk of rising liabilities related to around 6,000 pensioners and more future members living longer than expected.

Zurich in turn transferred a significant portion of the risk to Great-West Lifeco Inc.'s Canada Life Assurance Co.

Aon PLC acted as lead transaction adviser on both deals, negotiating the terms with Zurich and brokering the reinsurance deal with Canada Life.

The transaction is Zurich's largest longevity swap to date, the company's head of longevity risk transfer Greg Wenzerul said.