ian hislop
The satirical panel show debuted on BBC Two on 28 September 1990.
The PM's chief advisor was the subject of a "pitch perfect" monologue from the journalist and broadcaster.
The Netflix series' creator hosted the BBC panel show on Friday.
"Go out in the garden, have a bit of sunshine, and stop believing complete rubbish," the Have I Got News For You panellist said.
The topical BBC panel show has had to adapt due to social distancing rules.
Have I Got News For You descended into a tense row over Mercer's alleged links to a bust financial firm.
'Unless Ann Widdecombe has put off an entire gender, it's because they’ve said no.'
If we ignore all the problems in Britain will they just go away?
Ian Hislop looked totally unaware of what was happening behind him.
'Already? They’ve approved him?'