ALL ROADS LEAD AGAIN TO LONDON

Every late-spring and early summer morning this year, the tour and travel agent said, the Telex in his London office greeted him with a long scroll of cancellations being reported by his American partners.

There would be 30 a day, more than 500 altogether, and he and his staff, which had to be reduced by two-thirds, were kept busy undoing the bookings and arrangements they had been all winter making.

But by midsummer the tide had turned. There were late-season bookings and a healthy head start for 1987. Traveling in early August, it was actually hard to know where the downturn in tourist travel was. It took a slow and exasperating hour to check in at LAX--partly because of the volume, partly the more meticulous security arrangements (which I heard no one objecting to).

It was the better part of another hour, in a long, snaking line, to clear immigration at Heathrow. Outside London the crowds shuffling past the armor in the great houses were enormous, and a guide at one said they’d had 15,000 visitors the day before.

The newspapers and the telly were full of familiar glum tidings--unemployment and unrest, worries about the growth of a permanent underclass of British welfare families now into the third generation, more soccer hooliganism, this time in Amsterdam, where the visiting Brits tore the town apart after an unimportant exhibition match. The unemployment, the unrest, the young male frustration and the hooliganism are inevitably related.

But the problems are most severe in the north of England. London, glorious London, seems more than ever an oasis of bustling confidence. The air of prosperity does not appear to be merely window dressing for the tourists, although it is true that more of the great buildings have been de-grimed so that they almost glow in the summer sun, as if to please the guests.

The whole city occasionally presents itself as one long scaffolding, and the aromas of brick dust, cement and drying plaster are perfumes of prosperity as gentrification ripples out from the center of town and the prices of houses and flats read impressively, even by California standards.

The London financial community is about to begin operating under much-relaxed regulations and an in-rush of hot-shot investment types is already in progress. One symptom of an onrushing modernity, as several newspapers reported, is the decline in the wearing of the bowler hat. Only one firm in England still makes them, and they are frightfully expensive, as well as--one hates to say it--old hat. Still, hatless or not, London is a place for visitors, foreign and domestic. The British Museum is a cheerful international mob scene daily, and it’s your life to get a drink or a bite of lunch at one of the famous old Thames-side pubs.

And the theaters, now largely sustained by visitors, displayed everything but vacant seats so far as I could tell. There was a queue for standing room only for the Howard Brenton and David Hare comedy “Pravda� at the National Theatre.

It offers a roaringly energetic and deliberately hoarse-voiced performance by Anthony Hopkins as a South African newspaper tycoon invading London very much in the manner and mold of Rupert Murdoch. But the text is far less incisive about journalism than it might have been.

London’s newspapers, now in a tumultuous condition of change, are themselves big news these days, thanks partly but not entirely to Murdoch, and for the locals anyway the play has the aspect of an in-joke. The play could have mixed its scorn with a bit more alarm at the down-marketing of information.

Although it has had mixed reviews in London, as it did in the United States, Jonathan Miller’s production of Eugene O’Neill’s “A Long Day’s Journey Into Night,� starring Jack Lemmon, has been playing to capacity audiences in the historic Haymarket Theatre (more accurately, the Theatre Royal Haymarket).

Miller has (controversially) tried to tone down the O’Neill rhetoric to more naturalistic conversational cross-talk. It nicely fits Lemmon, whose strength as an actor has always been as Everyman, not a flamboyant matinee idol who might ever have trouped in “The Count of Monte Cristo.� But, ironically, it’s ultimately the size and grandeur of O’Neill’s passion and anger that asserts itself and makes the final curtain a deeply moving moment. There were wet eyes and much ado about handkerchiefs during the curtain calls.

The hottest ticket in town is evidently for “Les Miserables,� yet another triumph for Trevor Nunn (here co-directing with Jon Caird), who has given us “Nicholas Nickleby,� “Cats,� “Starlight Express� and another current London success, “Chess.�

The operatic adaptation of the Victor Hugo novel has more production credits than a tax-shelter movie, but Alain Boublil and Claude-Michel Schonberg conceived the project in Paris, where it opened in 1980. Schonberg did the music and Herbert Kretzmer, a longtime drama critic who now reviews television, did the English lyrics.

When it comes to monumental staging, Nunn is obviously nonpareil these days. Prisons, sewers and gunfights at the barricades appear as if by magic. But, alas, the music struck me as surpassingly banal and unrememberable. As with “Cats� and “Starlight Express,� you go out--as has been said--whistling the sets. There is not even the one grabbing ballad, which “Cats� does have. The power is in Hugo’s timeless story line.

In the matter of timeliness, dear old Shakespeare remains a rose by any identity, and the Royal Shakespeare Company’s romping production of “The Merry Wives of Windsor,� with Peter Jeffrey as Sir John Falstaff, is a reminder that the plays work in any century if you do them right.

This time Sir John does his bifocal courting and waddles about in contemporary dress at a moment, I would judge, somewhere west of flappers but east of jitterbugs. He still exits in a laundry basket and he is wonderful, farcical fun.