When two people involved in the same conversation have a completely diffferent recollection of it, how are the rest of us supposed to judge who is right? Well, judging from the responses on social media to the Nus Ghani allegations against the government chief whip Mark Spencer, everyone is falling back on their pre-conconceived ideas and bugger the truth.
If you're a tribal Conservative you come down on the side of the chief whip and assert that Nus Ghani was clearly a useless minister and that's why she was sacked. You think it's all part of a Remainer plot to get rid of Boris Johnson, and therefore the wagons must be circled.
Opponents of the Conservatives will tend to side with Nus Ghani because they believe most Conservatives are intrinsically racist or islamophobic and it's an institutional problem for the party and always has been.
But what about those of us who don't have a dog in this conflict. What about those of us who know both Ghani and Spencer? How do we judge who's right?
First of all, I remember the day Nus Ghani was sacked. In fact, let's go back further. Let's go back to the day Boris Johnson formed his government in July 2019. Given he got rid of most people who hadn't supported his leadership campaign, I was a little surprised Nus's services were retained. Maybe her support for Brexit saved her at that point. But I was equally surprised when she lost her job. She'd had a couple of difficult moments, but name me a minister that doesn't. She had been widely praised in the shipping sector, for instance, and there were plenty of people in the wider transport sector who were sorry to see her go. It also seemed odd to sack a muslim woman when she seemed to be doing OK.
When I spoke to her about her dismissal she seemed pretty phelgmatic and certainly didn't mention any concerns about it being for any other reason than the PM needed her to make way for someone else.
When I read her remarks last night on the Sunday Times website I was horrified. And still am.
Later on Mark Spencer, the chief whip, tweeted a complete denial. He admitted that he was the whip Ghani was referring to, but he denied saying any of the words attributed to him.
I've only met Mark Spencer once and he seemed a very nice, hail fellow well met kind of guy. Nothing would lead me to think he was capable of saying the words Nus Ghani attributed to him.
His denial made me think back to a slightly fraught conversation I once had with someone. It turned out that the other person and I had a completely different recollection of what was said, and just as importantly, what was meant.
I wonder whether that could have happened here.
Because if Nus Ghani is right, Mark Spencer's political career is over. And if Mark Spencer is right, he's calling Nus Ghani a liar.
How on earth does any formal investgation come to a definite conclusion?
Paging Sue Gray...