Policies set up before 1.1.2013 often had renewal commission built into them for the original adviser. Typically 2.5% pa of any ongoing premiums for life or pension policies or 0.5% pa of the fund value for investment policies. The cost of that was all accounted for in the charging structure of the plans, and if say the advising firm went out of business, then the insurance company simply kept the money, as generally there's no provision for altering the charges due to the policy provisions.
Adviser Charging is an explicit cost which is now transparently shown as a specific deduction, and so can be stopped, started or the rate altered at any time, and the policy owner has to agree to the amounts to be paid to the IFA firm.
It's a common thing for the renewal commission to be signed over to a new adviser, to offset the costs involved in dealing with a new client. However, if any IFAs receive any ongoing commission on policies transferred to their agency, they have to provide an ongoing service.