In the last few moments, it has emerged that Qantas flight QF9, which operates Perth to London Heathrow direct, is diverting to Singapore.

Courtesy of RadarBox.com, Qantas flight QF9 is heading northbound to Singapore, instead of north-west to continue its flight to London.
At this stage, it is unclear what the reason for the diversion is to Singapore, with no indication of emergency squawk at this time.
QF9 is being operated by VH-ZNC, a 5.4 year old Boeing 787-9 that was delivered to the carrier back in 2018.
This is a developing story. See below for more updates as they come in.
Update on the Qantas Perth-London Diversion into Singapore…

UPDATE #1 @ 1733 UK time – At this stage, Qantas flight QF9 is still cruising at 33,000 feet and needs to get a little closer before continuing its diversion into Singapore.
UPDATE #2 @ 1740 UK time – QF9 now has a recorded squawk code of “1265”, which doesn’t indicate an emergency of sorts, with whatever being the issue is under strong control and doesn’t warrant it. It could be the fact that the aircraft doesn’t have enough fuel to continue to London due to high headwinds.

UPDATE #3 @ 1803 UK time – QF9 has begun its descent into Singapore. Once again, we don’t know the official cause of the diversion, but all will be revealed in due time.

UPDATE #4 @ 1813 UK time – Qantas flight QF9 is passing through 10,000 feet as it gets ready for its approach into Singapore.

UPDATE #5 @ 1820 UK time – QF9 is now on final approach into Singapore Changi Airport, following the choice of diversion whilst enroute to London from Perth.

UPDATE #6 @ 1824 UK time – Qantas flight QF9 has safely completed its diversion into Singapore. The aircraft was supposed to be doing Perth to London Heathrow originally.