Stanley Johnson joked he 'broke lockdown' rules to visit the shops on the day son Boris Johnson's baby was born.
The 79-year-old appeared on Good Morning Britain to speak about VE Day and seeing his father's plane crash and burn into flames when he was just four years old.
Wilfred Johnson, who Prime Minister Boris Johnson's youngest son is named after, was awarded the DFC after his achievements in the RAF.
Stanley said that he was "thrilled" that Boris and Carrie Symonds had named his newborn baby after his father.
He said: "A wonderful strange feeling, actually, to see that this name is going to live on in this young boy."
Stanley admitted that Boris and Carrie hadn't told him that they were thinking of naming him Wilfred.
The PM's dad said: "I'm very glad that they didn't tell me because I would have got into terrible trouble with people saying he only put some money on him and so on and so forth.
"I actually broke the lockdown rule, I've got to say - well, my car was pretty much on empty anyway. But I said, 'There's bound to be something in the papers.'"
He continued to say that he drove to a petrol station, adding: "I said, 'I know I'm not really meant to be out buying a newspaper, I'm not sure if it's an essential journey but I just think there's something in the paper today about my 14th grandchild."
But not to worry Stanley - you can go out to buy a paper so you kept to the lockdown rule book.
Stanley said that he had seen "plenty of photos" of his grandchild and that Wilfred "looks very sweet".
Asked how Boris was doing, Stanley replied that he had spent most of the time in lockdown writing to letters about those concerned about his son.
He added: "It's been a very big lockdown for me."
*Good Morning Britain airs weekdays at 6am on ITV
