But there were also lighter moments.
Ross Cassidy, Mr Skripal’s friend and former neighbour in Salisbury, had a twinkle in his eye when recalling how they would drink and enjoy barbecues together.
"We certainly would,” he said with a grin.
He even raised reluctant smiles, and dare we say laughter, from the legal teams when he revealed that he may have exceeded the speed limit when bringing Sergei and Yulia back from Heathrow Airport.
He even reiterated the point when asked if he’d got home in very good time that evening.
He said: "Well as I said, I was speeding."
The counsel to the Inquiry, Andrew O’Connor KC, replied: "Well I wasn’t going to mention that Mr Cassidy."
One of the most striking accounts for us was from a paramedic, Ben Channon who was called to Charlie Rowley’s flat when he had fallen ill a few hours after Dawn Sturgess.
He was the first to make the point that he lived through the Salisbury poisonings and had seen it all happen.
He told the inquiry, yes, he was scared, for his patient, and for himself, and that fear was still evident in his testimony six years on.