This ties in with what
@saulan says a few posts ago. I wonder if the checks were lax because she had flown via somewhere else or whether they would have been just as bad if she'd flown direct.
Out of interest, I checked Sky Scanner for flights on the 16th from SA to the UK and didn't see a single flight that didn't put down outside SA before landing in the UK. A Google search tells me that BA, Virgin and SAA do fly direct though. If the clowns in charge aren't planning to count arrivals from SA that have made a layover as an arrival from SA (90+ at a guess) it's a scandal, but hey, they don't matter any more do they?