One of the lead surgeons behind the most complex operation ever undertaken in Australia is a New Zealander.

Andrew Greensmith is part of a 16-strong medical team attempting to separate the conjoined Bangladeshi twins Trishna and Krishna.

The operation at Melbourne's Royal Children's Hospital today will take at least 15 hours.

There is a 25 percent chance the sisters will die, a 50 percent chance they will suffer brain damage and a 25 percent chance the team will pull it off.

Mr Greensmith graduated from Otago University in 1993 with a degree in medicine and later qualified in plastic and reconstructive surgery in 2001. The now 40 year-old father of two has special interests in facial aesthetic surgery.