By Catherine Portland

There are many good things about dating older men, but being asked by a small child on the underground why I was kissing my dad was not one of them.

John was noticeably older than me, but he was not ancient. He had simply gone grey early and refused to submit to the tyranny of hair dye. Despite being just 35, he had one of those weathered faces - craggy and appealing. He had lived and it was etched in his features, which I liked to think of as a map of his experiences and a testament to his sagacity and all-round brilliance.

He was 12 years older than me but looked more like 20. The response to our relationship came as something of a surprise to me, bred as I have been on a diet of US rom coms in which nearly every leading man is a good bit older than his lady friend.

No-one bats an eyelid on the big screen. And Hollywood starlets Catherine Zeta Jones and Calista Flockhart have bagged themselves silver-locked husbands in real life, so I just assumed that age asymmetry was universally accepted.

The reason, surely, that Sex and the City caused such a sensation was because the sexually liberated behaviour of its protagonists was seen as inherently manly and the stars were of the fairer sex. Samantha dating younger men was an inversion of the norm.

Or so I thought.

It turns out that Hollywood is not just more liberal than mainstream American culture - it is also more tolerant than 21st-century Britain.

During our four months together, John and I became accustomed to the gawping and whispering that members of the public deemed fair game.

However, the response of our families was harder - and ultimately impossible - to bear. My parents felt John was taking advantage of me, despite us always operating on equal terms, to the extent that I would never let him pay for anything.

I tried to explain to them that John had never been an authority figure to me and that far from being domineering or patronising, he valued my opinions and spoke to me as though I was au fait with his research into genetics.

John's family, meanwhile, assumed I was a bit of fluff. They could not believe that I wasn't one of his students angling for a better project mark. On the sole occasion I visited his family home his mother asked me what bands I liked as though I were a pubescent teenager and adopted the careful enunciation one usually reserves for a toddler or foreigner, switching between this register and high-blown analysis of John's latest chapter.

The only words his Dad ever spoke to me were: 'Goodness, you're young aren't you.'

In the end it was too much and John and I caved in the face of the world's incomprehension. So much for this progressive, permissive society we're supposed to inhabit - challenge the status quo and you'll discover why the Daily Mail has such a high readership.