An announcement said Blackstone and TSSP would look to develop Kensington’s mortgage lending business and broader speciality finance capabilities.
The lender was launched in 1994 and put up for sale by South African banking group Investec earlier this year.
The £180m cash deal was confirmed by the bank this morning.
Former Shawbrook chief executive Ian Henderson will take over as group chief executive while Keith Street will continue to lead Kensington’s mortgage arm.
Investec, which plans to continue lending in the UK, said the sale would substantially reduce its non-core business.
David Blitzer, head of Blackstone Tactical Opportunities, said: “Kensington presents an exciting opportunity to back a high quality management team and to invest in the UK mortgage market.
“Kensington is a best-in-class specialist lender with an established track record in the UK and strong customer relationships. We will invest in growing the business in the mortgage space as well as extending the range of its activities in specialty finance.”
Ian Henderson, incoming group chief executive of Kensington, said: “I am delighted to join Kensington and look forward to working with Keith Street and the management team under new ownership. Kensington is an outstanding business and we will use its expertise and market position to broaden our product range for new and existing customers.”