The US owners of Towergate are targeting a $1.1bn (£890m) debt raise, while committing to London by making the capital the global base of the insurance broker's new umbrella firm.
Earlier this month, City stalwart Towergate merged with four other firms in the hope of challenging larger global players such as JLT and Willis Towers Watson.
US private equity backers HPS and Madison Dearborn (MDP) merged Autonet, Chase Templeton, Ryan Direct, Price Forbes and Towergate under a new banner called KIRS.
Today, KIRS launched a £800m bond alongside £90m of banking facilities.
The firm also said its global headquarters will be at 55 Bishopsgate, underlining the belief of its US private equity backers commitment to London despite the Brexit concerns.
David Ross, the former Towergate boss who was asked to lead the new group, said:
The unveiling of the KIRS vision is proving to be the momentous shake up of UK general insurance we always envisioned it would.
KIRS said the proceeds from the debt raise will be used to refinance existing debt and to fund the acquisition of Direct Group and Chase Templeton.
The new group will employ more than 5,000 people and generate around £2.8bn of gross written premiums.
The owners drafted in the former chief executive of the Financial Services Authority, John Tiner, to chair the group.
He said: "The management team has held a number of successful meetings with potential and existing investors globally over the course of the last couple of weeks. The response to the creation of the KIRS Group, given its ability to broaden its services to clients and provide a platform for further expansion has been positive."