Harry befriended Jack and provided counsel and support when Jack was unable to cope with being locked up for a crime he didn't commit, and defended him from more thuggish inmates such as Grant Manny.
A few weeks after Jack was acquitted, Harry was released, but his family weren't interested in taking him in, so he counted on Jack for giving him a bed for the night. After acquainting himself with Jack's children, he revealed the real reason why he's there - to give Jack £3000 in used notes. Jack was vehemently certain he doesn't want the money, and offered Harry to stay another night, but Harry felt he had to move on. That night, after saying goodbye to Harry, Jack went to bed, and was stunned to find Harry had left the money on his bedside table.