Nicholas Lander eats out for the first time in many years on a Sunday

At first glance it seemed to be business as usual in the dining room at The Square in Mayfair. The customers were having a good time; the waiting staff were bustling about with wine bottles, decanters and trays of intricate food and there was the buzz of a busy, well organised restaurant.

But there were a couple of tell-tale signs that this evening was out of the ordinary. Firstly, we had arrived earlier than usual at 19.30 to meet friends who were already there having flown in from Hong Kong. And, close to a table of Americans making the most of the unpasteurised cheeses on offer, was the rare sight of two single diners at separate tables, one reading a book and the other in conversation with those on the next table. What all this signified was that this was a Sunday evening.

Restaurants on both sides of the Atlantic now play to full houses on Sunday evenings, a significant change from a decade ago when the only places that used to open were indifferent pasta or steak houses and hotel diningrooms usually fielding their third brigade. Behind this transformation lies a series of changing social and economic factors about how and why we choose to eat out.

The first and most significant has been the increase in international air travel. For business people flying in long distance for a week's work in either London or New York, the routine is now arrival on the Sunday, a good meal and a bottle of wine un the early evening followed by the welcome opportunity to overcome jet lag.

Consequently, Sunday evening at Yumi, George Street, W1, one of my favourite Japanese restaurants, is the busiest night of the week as its owner, Yumiko Fujii, welcomes the many Japanese businessmen who have just arrived from Tokyo. Over in St James's Street, Chris Bodker, proprietor of Avenue welcomed similar numbers of Americans who had flown in, checked in to Duke's, The Ritz or The Stafford and strolled round the corner for a good dinner. Bodker summarised his Sunday evening customers as 'generally well dressed and courteous, a group who eat, drink and tip well.'

This particular market disappeared almost overnight after 11 September in response to the decline in air travel and more stringent corporate expense scrutiny but, as our experience at The Square evinced, Sunday evenings are now busy again and Bodker expects that by the summer this business will be back to normal.

Sunday evenings are also distinguished by one other remarkable trend: whilst they are not the busiest night of the week in terms of numbers served – because, for example, there is no pre- or post-theatre business in the West End and most of us like to be in bed not too late on a Sunday – they invariably produce the highest average spend of the week.

I gleaned this remarkable fact from Tim Hughes, now executive chef of the ultra-chic J Sheekey, Ivy and Le Caprice troika. However glamorous these places may be during the week, Sunday evenings are special. 'We always sell more of all of the expensive items, lobster, Dover sole and caviar on a Sunday night than any other time of the week. It's a really fun evening.' This fact and sentiment was confirmed by Dominic Ford, restaurant director for Harvey Nichols, who explained that Sunday evenings in their Oxo Tower restaurant may not be as frantic as the rest of the week but they do attract a well-heeled, pleasure-seeking crowd.

This is because, without any determined marketing effort, these restaurants now provide a service on a Sunday evening for several distinct markets.

The first, and possibly fastest growing sector, are those who either do not have children or whose children have grown up and left home. It is not just that most parents are so exhausted on a Sunday evening that the last thing they want to do is go out, however good the food may be, but there is the further complication of finding a babysitter as well as the fact that Sundays for families still revolve around the lunch table.

For the under 30s and over 55s, such exhaustion is probably not a fact of weekend life. Many more know how to eat and drink well and treat Sunday evening as an extremely relaxed occasion on which to indulge themselves and their partners.

The second sector, particularly beneficial to the growing number of neigbourhood restaurants open on a Sunday evening, are customers returning from a weekend in the country. Back in town, hungry and thirsty but with nothing in the fridge, it is this type of customer who keeps Kensington Place in Notting Hill, another of Bodker's resaturants, as busy as those in the West End and the brasseries of Paris.

In New York, according to Richard Coraine, director of Eleven Madison Park, busy Sunday evenings are due to a combination of different factors. 'People come out to eat earlier on a Sunday because they need to be at home later to make sure they catch The Sopranos or Sex in the City on TV. Eating out is almost like a ritual before these programmes. Secondly, because the availability of seats at prime time is more flexible on a Sunday evening than the rest of the week, our customers see Sunday as a chance to enjoy the full experience at the time they want to eat. That is why the average wine bill on a Sunday evening is second only to Thursday, the big night out for corporate diners on both sides of the Atlantic. The other contributory factor in the size of these wine bills is that Sunday evening has become a popular night out for groups of chefs and restaurateurs who have not been working that day.'

Many restaurants can now satisfy all these customers on a Sunday evening because of one other fundamental shift, this time in the quality of what they serve. Whilst in the past restaurateurs were at the mercy of wholesale markets and middlemen – hence the outdated maxim never to eat fish on a Monday – many now work directly with farmers, growers and fishermen who deliver seven days a week, weather permitting. Fresh fish, for example, comes up to London from Brixham, Devon early every Sunday morning.

Our Sunday evening at The Square was certainly as good as any weekday meal I have eaten there. I only hope that I do not have to wait seven years – until our youngest leaves school – before the next one.

Open Sunday

Yumi (tel 020 7935 8320), Avenue (tel 020 7321 2111), The Square (tel 020 7495 7100) and Kensington Place (tel 020 7727 3184), all in London.

Eleven Madison Park (tel 212 889 0905), Tabla (tel 212 889 0667), Babbo (tel 212 777 0303), Cafe Luxembourg (tel 212 873 7411), all in New York.

Brasserie Balzar (tel 01 43 54 13 67), Market (tel 01 56 43 50 90), Train Bleu (tel 01 43 43 09 06), Le Tour d'Argent (tel 01 43 54 23 31), all in Paris.