Inclusion Criteria:  Adult patients aged between 18 and 80 years Diagnosis of dyssynergic defaecation using Rome IV criteria Ability to understand written and spoken English Ability and willingness to give informed consent  Exclusion Criteria:  Paediatric patients (age under 18 years) Diagnosis of defined structural or metabolic diseases that could cause constipation, such as Hirschsprung's disease, Parkinson's disease, multiple sclerosis, hypothyroidism (untreated), diabetic neuropathy, muscular dystrophy, motor neurone diseases, spinal injury leading to paraplegia, cauda equina syndrome Psychiatric or physical inability to comply with the study protocol (including e-diary assessments) at investigator discretion. Contra-indications to BTXA such as allergies, pregnancy (or intention to become pregnant during study period), breastfeeding, generalised disorders of muscle activity, myasthenia gravis Contra-indications to infracoccygeal injection at injection site such as infection or pressure sore, spina bifida, pilonidal disease, bleeding disorders (including therapeutic anticoagulation) Morbid obesity (BMI ≥ 40) Defunctioning loop or end stoma in situ External rectal prolapse