You can substitute virtually any international airport into the description and it would be accurate from time to time.
Arrive mid-afternoon and you can queue that long to get through immigration in DFW for example then have another long queue just to get passed customs.
I'm also applying the usual translation filters 'extremely rude' staff are usually just doing their jobs and refusing to make exceptions that people feel entitled to.
Quite how individuals failure to have their liquids packed properly is a LHR problem I do not know.
I travel in/out of LHR a lot and see none of this rampant inefficiency and rudeness, but I do see a lot of people failing to make life easier for themselves and having unreasonable expectations not met.