Complex sentence: An investigation by the Metropolitan and City of London Police forces identified and arrested Gardstein's accomplices within two weeks, and they were informed that the final two members of the gang were hiding at 100 Sidney Street in Stepney.
Split into simpler sentences: An investigation by the Metropolitan and City of London Police forces identified Gardstein's accomplices who were arrested within two weeks. Police were informed that the final two members of the gang were hiding at 100 Sidney Street in Stepney.