Inclusion Criteria:

• Have Grade 3 or 4 haemorrhoids (external disease with or without significant internal component)
• Be scheduled for diathermy haemorroidectomy with ≥2 quadrant involvement
• Be medically fit for surgery
• Subjects must be aged 18 years or over and of the legal age of consent.
• If female, the subject must not be lactating and must be (a) post-menopausal, (b) surgically sterilised, or (c) have a negative pregnancy test result prior to entry into the study and will use adequate contraception for the duration of the study.
• Must have provided written informed consent to participate.

Exclusion Criteria:

• They have had surgery to the anus or rectum in the past 8 weeks
• Suffer from a chronic pain syndrome which requires regular narcotic analgesia
• Have anal fissures
• Have diagnosed Crohn's disease
• Allergic to metronidazole
• Are taking any prohibited medication.
• Deemed mentally incompetent
• Considered by their physician unlikely to be able to comply with the protocol.
• Taken part in an experimental drug study in the preceding three months.