Nancy Reagan and her eight-car motorcade drove 22 miles west of here last night for a party on the English country estate of Jack and Dru Heinz.

It came with: Grazing cows. A two-acre lake. Guests like actor Peter Ustinov and Evangeline Bruce, widow of the former American ambassador to Great Britain. Pictures of duck decoys. A grotto.

And the butler, of course. He used to work for Bing Crosby. He also told jokes.

"I fell in love with the butler," said Sheila Tate, the first lady's press secretary.

The party was the sole official event for Nancy Reagan on Day Two of her royal wedding week schedule. She spent a portion of the afternoon napping in her room at Winfield House, the American ambassador's residence. (Reporters having tea with Josephine Louis, the wife of Ambassador John Louis, were told to be quiet.) Later in the day, Nancy Reagan got up to prepare for the party.

The Heinzes, of the ketchup and benas kingdom, are hard-core Anglophiles. Their estate, built in 1948, has become something of an American outpost for flashy entertaining. Dru Heinz, the publisher of a poetry magazine, gives parties all the time. If you're American, significant and visiting London, you usually get invited.

This particular party was actually peripheral to the royal wedding, being the Heinzes' annual celebration at the end of Ascot races. The track was nearby, over fiedl, hedge and shiny Rolls-Royce.

Lots of them drove up the quarter-mile gravel drive to the Heinz estate. Jaguars were equally popular, as were much smaller Peugeots, their occupants sitting knees-up in the back seats as the chauffeurs motored along.

Inside the cars you could find a variety pack of guests, carefully balanced by the veteran hosts to include actors, politicians, journalists and some of the livelier members of English nobility.

David Frost was on the list, as were Princess Alexandra, the duke and duchess of Gloucester, the Aga Khan and Sir William Rees-Mogg, former editor of the London Times.

Nancy Ragan left Winfield House in a clammy London chill about 7 p.m. She wore a black and white Galanos gown. It had a halter top, and she looked like she was going to be freezing.

"Could ye wave, ma'am?" the British photographers yelled.

She waved gingerly.

"Again, ma'am," they yelled.

So she waved the other hand. Gingerly.

"You don't look tired," somebody else called out.

"Really?" said Nancy Reagan. "That's the nicest thing I've heard all day."

Dinner at the Heinz estate consisted of veal, gooseberries, new potatoes and black currant sorbet. It was served to aobut 70 people seated at round tables spread throughout several rooms. Nancy Reagan's room was red, warmed by a roaring fire.

There was dancing after dinner, and then at aobut 11:40 p.m. Nancy Reagan and her motorcade left. They were preceded by two horse-drawn carriages, clip-clopping down the drive and out into the countryside.