Diamond, who was forced to resign from Barclays in 2012 in the wake of the Libor rigging scandal, runs a private equity vehicle, Atlas Merchant Capital.
Atlas and QInvest made the £15.5m agreed bid today, as announced to the London Stock Exchange.
Matthew Hansen, head of UK and Europe for Atlas, said: “We believe there is significant opportunity for Atlas, in partnership with QInvest, to apply our operational skills and financial services expertise to enhance Panmure Gordon’s strong reputation and build a larger, successful boutique investment bank.
“This long-term stabilisation and development can only realistically be achieved as a private company, out of the glare of the public market and the effects of share price movement.”
QInvest has been invested in Panmure Gordon for more than seven years and said it was excited about the opportunity to develop the business and fulfil its potential.
Andrew Adcock, chairman of Panmure Gordon, said: “The independent Panmure Gordon directors believe that the cash consideration will be attractive in providing Panmure Gordon shareholders with an opportunity to exit at a significant premium to the current share price.
“Against the backdrop of a challenging macroeconomic environment, with the resultant market volatility which has in recent years impacted Panmure Gordon’s business, the independent Panmure Gordon directors believe that the scheme price reflects a fair and reasonable offer.”
