Sky News has learnt that Jim Durkin has been asked by Cenkos's board to stage a surprise comeback and replace Anthony Hotson, whose departure was announced on Tuesday.
Mr Durkin, a 35-year City veteran who was a founding shareholder in Cenkos, is expected to return as its chief executive later this year.
Sources close to the firm said his appointment was likely to be announced this week.
Mr Hotson, a former Bank of England economist, has spent just over a year in the role, a period marred by a slump in profits at a firm reliant on sizeable deals to boost its profitability.
A 90% fall in earnings led to a cut in Cenkos's dividend and added fuel to the argument of Crystal Amber, the broker's fifth-largest shareholder, that it requires an urgent change of direction.
Sky News revealed in July that Crystal Amber had written to Gerry Aherne, Cenkos's chairman, calling for him to launch a strategic review "to determine how value can best be realised".
It was unclear on Tuesday whether Richard Bernstein, the prominent investor who heads Crystal Amber, would be reassured by Mr Durkin's re-emergence at Cenkos.
A summer profit warning from the broker sent its shares plunging 12%, reinforcing the uncertainty surrounding many City firms as new European markets rules inhibit the range of activities from which they can derive revenues.
Cenkos is no stranger to boardroom uncertainty, with previous rows having claimed the scalps of a number of directors.
In its letter, Crystal Amber said: "We are concerned that the Cenkos franchise is struggling to build a broader, more recurring revenue base.
"Despite Brexit, London remains a pivotal financial centre.
"The existing platform can be an attractive springboard for a larger financial institution.
"Consequently, we propose that the Cenkos board should now commence a strategic review to determine how value can best be realised."
A major chunk of Cenkos's shares are held by employees, and it is far from certain that Crystal Amber would be able to force directors to conduct a strategic review without support from a large number of other independent shareholders.
The firm is one of the most prominent in the City, arranging company flotations, share sales and mergers including last year's listing of the logistics group Eddie Stobart and the 2014 initial public offering of the AA (Frankfurt: A116XA - news) .
However, it recently resigned as the broker to Stobart Group, the infrastructure conglomerate at the centre of a massive corporate governance dispute, and two years ago was fined for its work on Quindell (Berlin: 30382595.BE - news) , an insurance outsourcing business.
London's small- and mid-cap broking sector has been ravaged by new regulatory burdens and declining revenues, with analysts predicting a fresh wave of consolidation as firms seek to reduce costs and capacity.
A Cenkos spokesman declined to comment on Mr Durkin's impending reappointment.