Lady Morrison is nervous - her car boot sale is attracting thousands.
They have become known as Rolls Royce boot sales - a chance for hoi polloi to buy aristocratic junk from the owners of stately homes in their very own grounds. This year's is tomorrow, amid the 4,500 acres of Sir Charles and Lady Morrison's moated Madresfield Court, nestling at the bottom of the Malvern Hills.

Among the 120 booters, besides Lady Morrison and other local nobs, will be dealers from London and as far afield as Yorkshire and Cornwall. At pounds 30 a pitch, she is confident of keeping out the riff-raff with their dodgy videos and electrical appliances: but what of the expected 10,000 punters?

"I'm extremely nervous," she says. "In fact, I'm thinking of renting a Rottweiler. I believe these events can be horrendous - don't people claw at the car doors?"

Lady Morrison must be thinking of the notorious first Rolls Royce boot sale at Nostell Priory, west Yorkshire in 1993, which caused a 10-mile traffic jam. Some 15,000 people joined the scrimmage for booty and there was a spectacular tug-of-war over Lady St Oswald's fur coat.

Since then, the aristocratic grapevine has been passing on a trick or two designed to curb the rapaciousness of the lower classes. Lady Morrison's cousin, Lady Cotterell, made sure to have a tete-a-tete with Nostell's flummoxed Lady Oswald before holding her own successful car boot sale at Garnons, Herefordshire, two years ago (8,500 visitors' cars, grossing pounds 26,000, pounds 23,500 net, for the Samaritans).

Lady Cotterell's advice to her cousin's organising committee: "Have four lanes of cars at the entrance and charge a round fiver to avoid wasting time giving change. We put up a sign saying `Have your pounds 5 ready' and they all came whizzing in brandishing five pound notes.

"Charge pounds 2 for people on foot so that it's not worth their while abandoning their car outside. And get the police on your side so there's proper traffic control."

There is no chance of any Rembrandts or Constables being mistakenly given the boot, but Lady Morrison is auctioning a couple of dozen items donated mostly by local gentry: paintings, Royal Worcester china - and, yes, family silver. It will be a tender-only "silent auction" so that dealers do not have to quit their boots en masse and risk getting their kit nicked.

Richest pickings are likely to be among the 1,000 secondhand clothes boots - or "costume" to those who deal in it. Lady Cotterell's do raked in pounds 3,500 from costume alone. Clued-up dealers paid a few quid for ball gowns and cocktail dresses with designer labels from the Twenties to Fifties - Worth, Dior, Balenciaga - then sold them on for three-figure sums.

Lady Morrison's target for tomorrow: an attendance of 10,000 and a take of pounds 25,000 for St Richard's Hospice, Worcester. Besides catering and a licensed bar, there will be children's amusements, 20 craft stalls, a police band and free entry to the gardens and maze.

The cousins will both be manning their own car boots. Lady Morrison says she will start in Madresfield's attic and work her way down to the cellar, gathering pictures, china and books to display for sale in her Range Rover. Lady Cotterell promises that her Saab will offer "a load of rubbish", including unwanted Christmas presents, a ceramic inhaler, a Silver Jubilee commemorative mug and a china Hereford bull. It must be worth braving a scrimmage with the lower classes to get shot of that little lot.

Madresfield Court is signposted between Malvern and Worcester on the B4424. Entry: cars pounds 5, pedestrians pounds 2 (tomorrow 10.30am-4.30pm).