I just successfully snagged this fare from London Heathrow to Melbourne via Saigon in Vietnam Airlines business class for £1,658.77 all in directly from Vietnam Airlines' website.
https://goo.gl/flights/zQWL
It's their 787-9 dreamliner all four segments, fully flat beds.
For miles and plane junkies like me it's also possible to try out their A350 biz class with an extra leg Hanoi-Saigon for no extra money. Doing so should earn nearly 56k miles (I'm crediting to Alitalia).
Happy hunting!