Its all done electronically now, you don't see any Immigration officers.
You scan your passport and the gate opens in in to the UK you go .
Its been that way for at least five years now .
Previously the brown staff at Heathrow were more likely to be south Asian origin than Pakistani origin .
Quite likely their grandparents moved to the UK and they are more British than you are , they live and work in the UK and you live abroad.
Their taxes pay your pension money