Wouldn’t be surprised if ultimately LHR goes double daily ex-SYD before anywhere else in Europe or MEL/JFK.With 12 aircraft, that's enough for at least 5 pairs of routes flying daily, with spares.
So enough for SYD/LHR, MEL/LHR, SYD/JFK, MEL/JFK and SYD/CDG.
But, it will be interesting what schedules they end up with, assuming a 19 hr trip eastbound, in the Aussie winter, a 6am arrival into SYD would involve a 2am departure from LHR (or midnight departure in the Aussie summer). I guess, curfew permitting, a 1am departure ex LHR might work for a 5am into SYD. Otherwise it will be at the other end of the day - a 10am from LHR would reach SYD at 2pm, 3pm or 4pm, depending on time of year.