Efficacy of local anaesthetic transversus abdominis plane (TAP) blocks in laparoscopic colorectal surgery

Study hypothesis: There is no difference in post-operative morphine requirements between patients receiving a transversus abdominis plane block versus placebo in elective laparoscopic colorectal surgery.
Primary outcome(s): Post-operative morphine requirement measured in mg via a patient controlled system and analysed according to mg/kg, assessed according to usage at 1, 12, 24 and 48 hours after the patient wakes up from the anaesthetic.