The platform will help nearly 5,000 advisers with retirement planning for almost 250,000 clients, the business said.

Richard Rowney, chief executive of Nucleus, said: “Today we welcome our new colleagues to the Nucleus Group and we’re excited to start work on bringing our businesses together.”

He said the deal was an important milestone for the business.

“It helps us to build on our position as a key player in the market, enabling us to continue to invest in the priorities of advisers, and deliver our purpose of helping make retirement more rewarding.”

Peter Docherty, interim chief executive of Curtis Banks, said: “The completion means we can now harness the opportunities it brings and be able to offer advisers access to a broader suite of platform services, while continuing to offer both our on and off platform services, a larger customer support function and have the ability to invest in the business.”

In July Nucleus self-referred the merger to the CMA which said earlier this month it would not launch an investigation into the deal as it did not present competition issues.

The FCA, PRA, and Solicitors Regulation Authority had earlier issued their approvals of the merger.

For the immediate future both businesses will continue to operate independently and there will be no change for advisers or customers of either business. Curtis Banks will eventually be rebranded under the Nucleus banner.