'The 9' pre-COVID-19 used to mostly be punctual, but it and return working QF10 have somewhat deteriorated in recent weeks, though not as badly as QF1/QF2 that operate on a different route to LHR.
On Tuesday 26 July, QF9 (B789 VH-ZNJ) took off in MEL at 1627, 72 minutes after the scheduled mid afternoon 1515 hours pushback. PER arrival is suggested as 1808 hours, 53 minutes late.
Monday 25 July's QF1 (A388 VH-OQJ) arrived LHR on Tuesday 26 at 0744, 69 minutes behind its timetable.
A388 VH-OQD departed as QF1 in SYD at 1736 hours, 101 minutes late. In SYD, the east-west runway is in use for arrivals, so it's slowing ops down. While QF1 was waiting for takeoff clearance at the end of runway 34L, QF2230 ex WGA touched down (Q400 VH-QOM) on runway 25 at 1806 hours, 46 minutes late, as did other following flights such as VA530 ex OOL that's about 68 minutes late. QF475 (B738 VH-VZLK, the 1730 hours SYD down to MEL) also used the east-west runway to become airborne at 1815 hours.
SQ242, the A359 9V-SHS as the 1805 hours SYD - SIN was able to use the east-west runway and take off at 1819, ahead of QF1 even though the latter had been off blocks much earlier and was still sitting at the south end of the airfield. ATC will have safety and then orderly aircraft ops as #1 and #2 in their mind, and there was a stack of aircraft behind the SQ flight waiting their turn to take off, plus the usual priority to arrivals over departures, but it seemed a tad incongruous that the 'big bird of the skies', already significantly late, had to be usurped by its chief competitor operating a jet with lower seating capacity.
QF1 was eventually airborne at 1822 hours on 26 July. SIN arrival is estimated as 2356 hours, 106 minutes late, so an on time arrival into LHR tomorrow morning local time is impossible.
In contrast, SQ242 that was (to my eyes) given priority is due into SIN on the stroke of midnight, 20 minutes early.