The cabin crew themselves must have suffered through the flight - and they couldn't even strip down to the bare minimum!
Wonder why the airline decided to fly back to HK instead of finding the nearest international airport? I mean, it was 4 hours on before the pilot decided to turn back, which meant another 4 hours of torture in the hot cabin...!
EDITED to add an excerpt from the SCMP:
A Cathay Pacific spokeswoman said a valve in one of the plane's air-conditioning systems was faulty.
The flight turned back to Hong Kong at 2.52am, two hours after takeoff, and landed at Chek Lap Kok at 4.26am. Passengers boarded a replacement plane at 9am.
So the aircraft turned back after 2 hours, and not 4 as reported above by OP.