What does Mary Whitehouse often do while she's eating dinner? She watches television (if there's something suitable on, of course). John Sessions, on the other hand, never does. These days there are more of us who behave like her than him.
John Sessions is spewing out a torrent of bile which sums up his opinion of society's most pervasive vice. Sex? Cars? Drugs? No. The thing that really scares actor Sessions is ... eating dinner in front of the telly.

"I hate it," he fizzes. "I did it last night with friends, they asked me for a meal and there was a lot of telly blaring and I didn't like it at all. Television is the opiate of mealtimes. It's a mainline narcotic which I avoid. I'm one of those people who select what they watch - maybe 10 programmes a week. Why do people do it? Because it takes away the awful silences. When you can think of nothing to say to your wife or children you are comforted by the fact that you can cast an eye on Dale Winton..."

Here's the sting: if you think Sessions is over the top then you are part of a new and growing moral majority. A survey for market analysts Key Note recently found that two-thirds of Britons eat their evening meal in front of the television and the trend is increasing. The family meal is dying on its sofas. All those end-of-day catch-ups; all that witty banter. Gone.

There's a confusion here, surely? When Sessions erupts he is voicing something that is probably instinctive in all of us - because telly-dining arguably threatens virtues we would otherwise support: communication, the sensible division of pleasures, family life...

Yet everybody's at it. Not just on paper, and not just the masses. Researching this article I spoke to a leading member of the Arts Council, an entrepreneur, a literary agent, a nutritionist, and most ironically of all - that arch campaigner against TV values, Mary Whitehouse. All admitted that to some degree they are guilty of TV dining.

My own feeling is that Sessions is right: the habit threatens to make Teletubbies of us all. But in the face of that kind of evidence it is clearly time to look at the defence. And the fact is, it's impressive.

Item: Juliet Burton. She's a pleasant, attractive London literary agent with a husband and nine-year-old daughter to go home to. But does she TV-dine? "Yes," she says, "I'm embarrassed to say it but I have to be honest. I would say, five nights out of seven. Usually, my daughter Gemma will have her grub and sit in front of the TV and I'm drinking heavily while Michael will still be working upstairs ... and then usually, we'll have ours watching telly too."

Why? "It's a habit we got into when we went out all the time and were never at home in the evening. We would be out at the pub - even at cultural events - and get home and have a quick snack in front of the TV. That's how it started. Then when Gemma was born we stopped going out but the habit was ingrained by then."

So it's the product of an active social life, clearly tweaked by exhausting days. Fair enough, though Ms Burton admits: "I think it's pretty awful," and when you ask why not stop and just talk, she says, "We talk over telly all the time anyway."

Move on. Gillian Brierley is development manager for the Academy of St. Martin in the Fields. She's 30, lives alone and eats at home maybe three times a week: "I do eat in front of the telly when I'm by myself," she admits. "Not always, but the majority of the time."

Why? "Eating in silence makes you terribly aware that you are by yourself and silence can be quite a harrowing thing." How about music? "Television is more instantly engaging than the radio. It's right there in your face."

So TV is a partner, too. The virtues mount. Gavin Henderson is principle of Trinity College of Music, and chairman of the Arts Council's music panel. "I'm married to a TV producer so to that extent TV features in our lives, except I don't watch very much," he says. "But when I do, it is true, I tend to eat with it. It tends to be a video because I go to live music programmes almost every night and it tends to be with a take- away Chinese meal."

Isn't he, of all arty people, ashamed of himself? "Not in the least. I sort of feel guilty that I don't watch more TV because of the notion of popular culture."

So what does he watch? "I have a certain guilt that I spend so much of my time going to quite demanding performances that when I watch TV I love crap. I love retinal massage. Stuff that floats in front of my eyes. The Bill, for instance."

Complaints elsewhere, please, but you see the point. For Mr Henderson, TV meals amount to research and - as perhaps with Ms Burton - a kind of therapy. It's almost noble.

John Standing owns a catering business in Brighton, and he has good reasons to watch, too: "I have been living with someone in the past and in that scenario we used to sit down and exchange thoughts at the end of the day," he says. "But now I tend to walk in and rather than just be in the house with nothing I may have TV on - Sky News or something in the background. If I'm going to eat around the time the news comes on I will probably take my dinner in and watch. But it's more a time management thing as well."

Hurry on to Mrs Whitehouse. From her I was expecting an earful. Not a bit of it. "I think a lot depends on what is on," she said. "As far as we are concerned, my husband and I want to watch the news and if that comes on at the same time as our meal then we will watch it while we have our meal."

And there we are. Defence rests. Everyone has a good reason to eat in front of the television for at least part of every week. It is a habit ingrained by the good life, it is company, efficiency, cultural investigation, news concern and efficient time management.

But of course, the whole point about pervasive pleasures is that they find several levels of justification. What would the prosecution say?

John Sessions traces his own resentment back to childhood memories of Vietnam war coverage. "My parents always had the TV on at mealtimes and I was aware that there was something wrong with sitting there eating a burger with these images of GIs hauling through the jungle going on in the corner," he recalls. "I thought it was crazy, eating at the same time."

But many of those who now watch and eat clearly don't care what's on. Indeed, some view news as a more worthy accompaniment to food than, say, Absolutely Animals. Have we grown less sensitive? Or do TV dinners simply underline - even protect - the blandness of what we watch? These are questions the prosecution might ask. And then there's the meal itself.

Dr Michele Sadler of the British Nutrition Foundation says of TV dining: "You are focusing less on the food. There's no evidence that that has any effect on nutrient intake, but in terms of satisfaction you get from eating, if you see less, might you want to go and seek that satisfaction later? Maybe that should be investigated." Maybe it should. But Dr. Sadler says she TV dines "occasionally".

Sessions says he wishes he could be as funny professionally as he is over dinner with friends. Maybe any of us should ask ourselves when we last cracked a joke over telly. And singles might ask themselves when else in the day they experience silence. "It's just putting the problem on hold," is Sessions's view.

Personally, I'm with the prosecution. Too many mingled pleasures, one is never enough. Evidence: a ubiquitous can of Coke; an ever-present Sony Walkman. TV dining at any level other than the most occasional is just another monument to greed.

Sentence? Make it community service. Eat with friends. Bring back candles and napkins and serviette rings and lacy table-cloths. Dress up the meal like some old partner who's run out of sexy ideas. Reach for the radio. Anything rather than the TV knob. You won't agree, of course. But then your sofa is probably stained with gravy.