There's a description of what happened on pages 412 - 414 of Wilkes book, basically, JB wanted to commission Macdonnell and did a deal with the Sunday Sport to raise money (wouldn't have thought that was possible). The money was shared between himself and a go between but JBs share soon ran out. Wilkes then did a deal with JB whereby he would have access to the defence files in return for commissioning the report to JBs specification.