Data Migration from Bespoke ERP to Business Central

Customer had Bespoke ERP which was developed by inhouse and external developer using SQL Server as backend in an incremental manner thus there was lot of data inconsistency in the system. Apart from that client had one part of business which they have acquired in past was still using Microsoft Dynamics GP. Client wanted merge and streamline data from both sources into Business Central and at the same time wanted to clean it up as well.