A 48-year-old woman with a 15-pack-year smoking history presents with persistent vaginal bleeding and a visible cervical lesion on speculum examination. Cervical biopsy confirms squamous cell carcinoma, stage IB1 (tumour size 2.5 cm, no parametrial involvement). She undergoes radical hysterectomy with pelvic lymphadenectomy. Histopathology reveals tumour invading the outer third of the cervical stroma with 2 out of 15 pelvic lymph nodes involved. According to current FIGO 2009 staging, what is the most appropriate stage for this patient?