Last week I met two 80-year-old men who each gave me a piece of their mind.

One was a vegan activist, campaigning for the animal rights group Viva! in our city centre. He told me he’d been a vegan for 15 years and offered to get down, right there in the street, and give me 10 push-ups. I was happy to take his word for it.

The other octogenarian was a Welsh beef and sheep farmer. I suggested to him that a vegan diet can be very healthy. He fixed me with piercing blue eyes and raised his voice: “I feel fit as a fiddle and I’ve been eating meat all my life, seven days a week!”

I can’t imagine these men ever having a conversation, finding any common ground or even the slightest ounce of respect for one another. They perch determinedly on opposite ends of a political spectrum, a fierce ideological battle raging between them.

Yet, physically, they had much in common. Slim, strong-looking men; standing tall and straight with sparkly eyes that hadn’t dulled with age.

It made me think a long and healthy life may have less to do with what you eat, and more to do with your own spirit and steeliness. Believe passionately enough in something and you’ll be shouting at the younger generation well into your eighties.