"When enquiries to individual companies failed to persuade them to disclose the information, we submitted complaints to Companies House, forcing companies to re-file their annual returns with the information included, and sparking Vince Cable to announce the launch of an investigation. ... Having compiled a full set of subsidiary listings, ActionAid was assisted by company information specialists www.duedil.com to process the data into a useable format. The annual returns, which in most cases were available only as scanned PDF files from Companies House, were converted to text using Optical Character Recognition (OCR) software, after which extensive corrections were made."