There are always lessons to be learnt from spending time with my in-laws.

This week, after five days in their company, I am determined never, ever in my life to use the phrase: "Things were so much better in my day."

My husband's parents, like many of their generation, frequently point out that this country has gone to the dogs.

They cite examples of violent crime, political sleaze, drug-taking youngsters and child abuse to support their views and then make comparisons to an age when you could leave your back door unlocked without fear of being burgled and when teenagers didn't exist.

If they start on this vitriolic rant, my husband and I usually let them get it off their chests without making any comments of our own.

Whether we agree with them or not, we remind ourselves there's little point in proffering alternative viewpoints.

We then try to introduce a more anodyne topic of conversation, although I have known his parents turn a casual remark one of us may make about how nice the carrots are in our local greengrocer's into an opportunity to have a go at "that awful Tony Blair".

However, this week, for some confounding reason, my internal switch malfunctioned and I found myself retaliating while they were still in full flow.

What made it worse was that we were in a public place - one of Brighton's classier seafront hotels - and it was their wedding anniversary.

I'm not sure what got into me. I've been blaming my mood swings and lack of patience on my pregnancy.

Perhaps my sheer bulk and the fear I'm engendering in others gave me the courage to speak out.

In any case, I couldn't let my father-in-law's attacks on "people who don't dress up for dinner" - it was clearly a dress-down Monday for most of our fellow diners - go unchallenged.

"Why should people have to dress up?" I began.

"Because if they don't, it shows a lack of respect," he said. "It might seem a small thing to you but it's an indication of how far standards have dropped."

"The fact that people aren't wearing ties doesn't mean they're about to mug you," I tried pointing out.

He glanced at some of the casually-attired people on nearby tables and muttered: "I wouldn't be so sure. You'd better keep a tight hold on your handbag."

At this stage I should have let it lie but I didn't.

"I don't think standards have dropped - it's just that they've changed. The world isn't a worse place compared with when you were younger."

"Oh yes it is," joined in my mother-in-law. "Look at the problems we've got now with asylum seekers and paedophiles and terrorists - and that awful Tony Blair."

"But social problems have always existed," I said. "They're just different problems now to the ones your generation faced."

By now, my in-laws were already talking over me and quoting various examples of recent shocking events that confirmed their opinions.

All I had succeeded in doing was fuelling their attack so I turned my attentions to the decaf coffee and mints that had just arrived at our table.

My husband, meanwhile, attempted to steer the conversation towards more neutral territory and thought that reminding his parents of their wedding day would be a suitable opening gambit.

"Yes, it was lovely," said his mother quickly. "But it's a disgrace these days that so many people are getting divorced - or not getting married in the first place."

"Yes, shocking," I acquiesced.