A 62-year-old man presents with a 3-month history of alternating constipation and diarrhoea, with blood-stained stools and weight loss of 4 kg. On examination, a palpable mass is felt in the left lower abdomen. Colonoscopy reveals a stenosing lesion at the rectosigmoid junction with biopsy confirming adenocarcinoma. CT staging shows tumour confined to the bowel wall with no distant metastases. The patient is fit for surgery. Which of the following is the most appropriate surgical approach for this patient?