At the party to open a happening new club? On the set of the movie Nightmare at Central Casting? Wrong and wrong.
They will be at the preview day of the Chelsea Flower Show, mugging for the cameras in the hope - seldom fulfilled - of getting into Tuesday's papers.
Their eager presence proves that Chelsea, once a rarefied social occasion for the upper crust, has fallen victim to modern Celeb Culture.
It has been a gradual process. Until 10 years or so ago, the people invited to open exhibits were the kind who usually had roses named after them - dames, such as Vera Lynn and Anna Neagle, and one or two game duchesses. Some believe that the rot set in when a pink-and-cream sweet pea was named after Terry Wogan in 1983.
It is not that Chelsea is attracting more visitors: the capacity of the grounds of the Royal Hospital means that attendance is always limited to 180,000 on the four members' and public days, Tuesday to Friday.
The reason for the mounting hype is that growers who spend all year preparing their exhibits, and firms which invest up to pounds 200,000 in sponsoring show gardens, insist that their publicity reaches the masses who, in their pocket-handkerchief back yards, make gardening Britain's most popular leisure pastime.
The result is that press day at Chelsea becomes every year more and more like press day at the Motor Show; and it is no coincidence that cars will figure in several of tomorrow's stunts. A 1928 Morgan Super Sports Aero three-wheeler will sputter into one of the show gardens, sponsored by an insurance company to celebrate the 66th anniversary of the introduction of compulsory motor insurance. Nearby, a Model-T Ford will be on view in a so-called Globetrotters' Garden, while two classic cars will feature in the Garden of Honesty, part sponsored by Skoda.
In the marquee, Birmingham City Council will present a life-size model of the new Jaguar XJ220 in carpet bedding - already a firm favourite for the title of the most seriously naff exhibit in the show.
Betty Boothroyd and Lady Solti will be first in front of the cameras, bravely trying to look their best at 8.30am. Madam Speaker, who had a rose named after her last week, will be introducing a white pea called Elegance, while Lady Solti will launch the Lilian Baylis rose, honouring the founder of the Old Vic theatre.
Esther Rantzen appears at 10am with an orchid called Childline Caritas, clashing with weather forecaster Suzanne Charlton and the rose Bobby's Girl.
Jonathan Dimbleby and his wife, Bel Mooney, will launch the rose Scepter'd Isle, honouring the Council for the Protection of Rural England - but to catch them you must miss Rosemary Ford, statuesque presenter of Come Dancing, fondling a rose called Sweet Memories and handing a cheque to Great Ormond Street hospital. The Bishop of Norwich will celebrate the rose Norwich Cathedral, but the reverent tone will not last. Martin Clunes, Leslie Ash and Neil Morrissey, from Men Behaving Badly, will get up to rude mischief in You magazine's kitchen garden.
Hello! magazine sponsors the Positive Retirement Garden for Help the Aged, while British Sky Broadcasting, in its first appearance at Chelsea, is represented by a New England Cottage Garden, "a mix of spontaneity, whimsy and good old-fashioned common sense".
If more proof were needed of Chelsea's plunge down-market, Miss England, Angie Bowness, will launch the Toro Wheel Horse Classic rose, "a compact floribunda with pointed buds" named after a lawnmower. Bring back Dame Vera.
The second part of Michael Leapman's "Gardening in the Landscape" is in the Sunday Review.