Hundreds of staff at Pension Insurance Corporation (PIC) are set to share in a windfall of up £250 million after the fast-growing pensions buyout firm was sold to a privately-owned European insurer for £5.7 billion.

The sale to Athora, an insurance business minority-owned by private equity house Apollo, is regarded as the biggest takeover deal in the UK this year.

Filings at Companies House indicate that about 280 individuals own shares in PIC, including the chief executive, Tracy Blackwell, whose stake appears to be worth an estimated £25 million.

Mike Wells, CEO of Prudential Plc, in a portrait.

Athora is run by Mike Wells, a former chief executive of the FTSE 100 insurance group Prudential

GETTY

A former Goldman Sachs banker, she was one of the first five employees of PIC when it was set up 20 years ago by the financiers Edi and Danny Truell. The business, known for its penguin logo, now employs 600 people.

PIC buys out workplace pensions and essentially takes on the risk of the schemes. It then makes investments in major infrastructure projects such as affordable housing, urban regeneration projects and renewable energy.

These are types of projects that chancellor Rachel Reeves has been encouraging the pension fund industry to back. She welcomed the takeover by Athora as a sign that “Britain is attracting billions of pounds of investment”.

“In particular, we welcome investment in housing and infrastructure so that businesses can expand and communities can prosper in all parts of the country,” said Reeves.

PIC manages £50.9 billion for 400,000 people and has invested £30 billion in the UK. It has bought out the pension schemes of major companies such as Next and Rentokil.

The transaction with Athora means that PIC will be owned by a single owner for the first time.

Reinet Investments, backed by the South African billionaire Johann Rupert, owned 49.9 per cent of the business. It said that since it invested in 2012 there had been a 900 per cent increase in the size of the firm.

Other notable investors were CVC, the Abu Dhabi sovereign wealth fund ADIA and HPS Investment Partners. Staff and other shareholders had a stake of about 4.5 per cent.

Blackwell’s retirement from PIC was announced in February. She had spent 10 years as chief executive. She is expected to stay on as an adviser to Athora.

When the deal was announced on Thursday she described it as “amazing growth story over the past two decades”.

Athora is run by Mike Wells, a former chief executive of the FTSE 100 insurance group Prudential. PIC will become the largest subsidiary in the business and also retain its brand.

PIC did not comment on the potential size of the stakes.