Samuels departed after close to seven years at the helm to start a new finance venture which doesn’t involve real estate and will not directly compete with Dragonfly.
Posniak has worked a number of roles since joining the lender in 2010, including his most recent one as head of sales and marketing.
Samuels said: “In Dragonfly I am proud to leave behind a fantastic business full of hard working and dedicated professionals.
“I have no doubt the business will continue to thrive as it builds on its success to date.”
Simon Rogerson, chief executive of Octopus Investments, Dragonfly’s parent group, said: “Dragonfly is a great, award-winning business that continues to go from strength to strength and I would like to thank Jonathan for all of his hard work over the years.
“He has built a first class business supported by a talented team and we wish him all the best for his new venture. Dragonfly’s strategy will remain unchanged and we look forward to continuing to grow the commercial and residential property lending businesses under Mark’s leadership."
Dragonfly completed a record £1.5bn worth of loans in the first six months of 2015, while the bridging lender has launched a recruitment drive to add to its team of 22.