The agreement, worth a new high of £22m, covers roughly 20 of the highest liability members in the defined benefit scheme.
Partnership is increasingly insuring DB liabilities through more targeted medical underwriting, but this buy-in is expected to be the first of many larger deals in the market.
James Mullins, partner and head of buy-out solutions at Hymans Robertson, said he “strongly” predicted that the market would grow further in years to come.
He added: “For trustees and sponsoring employers understandably concerned about their concentration of risk, an enhanced buy-in is a tailored and cost effective way of managing their scheme’s liabilities.”
David Harvey, head of de-risking solutions at Partnership, said the unprecedented size of the deal demonstrates how medical underwriting can play a “significant” role in de-risking schemes of any size.