ITV has shared a press pack for series 8 of Law and Order: UK. Episode 6 (Joseph's episode), doesn't feature in the series details, sadly, but his name is mentioned. 

An array of guest stars including Helen Baxendale, Hattie Morahan, Joseph Millson, the late Roger Lloyd Pack, Colin Salmon, Roy Hudd, Christopher Fulford, Haydn Gwynne and Harriet Walter join the cast for this season.