In the wake of the news, 3i stock rose as much as 4.9% to 214 pence ($3.40) in early trading, but the shares later settled back to trade at 211.7 pence by early afternoon, as analysts and investors took a closer look at the firm's lackluster financials.

"The quarter to the end of March appears to have seen flattish returns," Oriel Securities Ltd.'s Iain Scouller said in a note released in response to 3i's pre-close statement, issued at the same time as Queen's announcement. "Whilst there may be some positive benefit from higher earnings multiples, we expect much of this to be offset by weaker earnings, especially at European investments."

Queen, who took over as CEO after ousting Philip Yea in January 2009, said he will step down once a successor is found. He has worked hard to deleverage the balance sheet, which was burdened with £2.1 billion of net debt on Yea's departure. (Net debt jumped to £453 million at the end of February from £395 million on Dec. 31, 2011).

But 3i still trades at a hefty discount to net asset value, and there have been regular rumors that it could be a takeover candidate.

Queen followed the initial palace coup with a series of debt reduction measures, including the sale of a stake in its infrastructure affiliate, the liquidation of 3i Quoted Private Equity plc, (which brought additional cash into the parent's coffers) and the raising of about £735 million from a share issue in 2009, as well as the sale of its remaining venture portfolio.

He followed up with a management reshuffle in September 2010, which left the firm's long-serving buyout chief, Jonathan Russell, without a job and allowed Queen to bring buyouts and growth capital under one chain of command. The acquisition in 2010 of Mizuho Investment Management (U.K.) Ltd., the British debt management arm of Mizuho Corporate Bank Ltd., restored a third business line to the company after the closure of the venture unit, and completed the restructuring. 3i's business model now rests on a tripod of private equity, infrastructure and debt management.

Yet in recent months 3i has been seen to drift, with its shares still at a substantial discount to Sept. 30 NAV of 294 pence per share and J.P. Morgan Cazenove Ltd.'s estimated March 31 NAV for the company of 284 pence.

Welcoming Queen's announcement, J.P. Morgan Cazenove's Christopher Brown said: "The management change opens the door to a more radical approach."

Scouller made a similar assessment. "A change of leadership allows some reassessment of strategy, which we view positively," he said.

3i will announce its results for the full April-March financial year in May. But in its pre-close statement for the 11 months to Feb. 29, it said investments totaled £623 million, up from £581 million in the same period last year. Of this, £374 million was new investment, £89 million was further investment in the portfolio, and the balance was capitalized interest. Realization proceeds for the first 11 months totaled £764 million (2011: £491 million).