Alyssa Nolan leads prayers for conjoined twins Trishna and Krishna

 Alyssa Nolan, pictured here with mum Mary, has had 40 operations since being separated from her conjoined twin. 

The extremely complicated operation to separate the twins who are joined at the head, began as scheduled at the Royal Children's Hospital in Melbourne at 8.30am (AEDT) and is expected to take 16 hours.