yesterday took a 51 percent stake in Lloyd's of London insurance managing agent the Brockbank Group Plc.

The 50 million ($77 million) capital injection from the reinsurer will be used to create an enlarged Brockbank, combining the existing managing agency businesses with two new insurance syndicates for corporate investors.

Brockbank will have a 49 percent holding in the expanded company.

Agents of the Lloyd's of London insurance market have been seeking corporate investors to boost, or maintain, their underwriting capacity as individual investors, called "Names,'' withdraw from the market. Some names have been ruined by the market's recent losses.

As capacity declines, an agent's ability, and therefore the market's ability, to underwrite insurance risk is diminished, so companies seeking insurance may turn to other markets to fulfil their insurance needs.

"Despite the well-publicised difficulties experienced by the Lloyd's insurance market, Brockbank has in recent years been able to demonstrate its ability to grow profitably, delivering repeatedly above-average returns for names,'' Brockbank Chief Executive Mark Brockbank said in a prepared statement.

"In order to support this growth further, we have long stated our wish to attract a suitable corporate capital partner,'' he said.

The company warns that should "certain events'' related to the Lloyd's reconstruction and renewal package have an adverse effect on the Lloyd's market or on Brockbank before September 1, 1996, the arrangement can be unwound.

Investors in the market will vote on Lloyd's 2.8 billion debt relief and settlement package next spring. The plan is intended to end litigation and refinance and reconstruct Lloyd's following five years of losses totalling 8 billion through 1992, the last year for which Lloyd's has reported its accounts.

Should the plan be successful, Mid Ocean will make an offer, based on independent valuation, for all outstanding shares in Brockbank by September 1, 1997.

Brockbank is one of the largest managing agencies at Lloyd's with 450 million of premium income in 1995. The company said its two main syndicates, writing marine, property and aviation insurance, have been consistently profitable.

Brockbank also manages a syndicate that began providing capital in 1994 for automobile insurance written by Admiral, which sells policies by telephone direct to customers.

The arrangement is subject to shareholder approval and Lloyd's final consent.

Brockbank has received approval from holders of 56.7 percent of its shares.