The door is a portcullis affair of the type that usually comes with a moat. Game cocks preen themselves nearby, scratching in the Kent sunshine, their feathers glinting in the light reflected in the ancient mullioned windows.

It all once belonged to England's Black Prince Edward but now it is the property of Prince and Princess Andrew Romanoff. It's a little expensive to heat these days, and as a result London limousines have been scrunching up the drive, bringing luncheon guests who don't mind plunking down $25 a head to dine with the grandson of the dowager empress of Russia and his wife.

An hour and three-quarters from London you can step into a world in which Edward VII is Uncle Bertie and Rasputin a family friend. You can sit down to cold pheasant and smoked salmon while you listen to what the princess' mother told the duchess of Kent about the size of the jewels in the court of St. James and how Lady Mountbatten, aunt of Prince Philip, is really one giggle.

The princess is old-shoe and as effervescent as Perrier water. She is the prince's second wife - his first died in World War II. When she got engaged to him she had to learn to chart of the crowned heads of Europe eight generations back, because everybodt is related. "I rebelled after eight generations," she says, adjusting her charm bracelets and smiling. But she's got it all down pat now, occasionally even arguing it out with the prince, now 82 and a tad deaf, but totally charming.

Luncheon is served at a mirrored table that appears to be 50 feet long. The enormous candelabras are copies of the ones the latest Kremlin tenants seized, and the coffin-like clock in the corner was rescued from the royal hunting lodge in Finland. Royalty in family album-type snapshots adorn the tables - Queen Elizatbeth at perhaps 5, clearly bored to death at a reception and swinging her short legs absently from a chair, the czar himself wearing his shooting jacket and squinting into the sun.

"Let's drink till Phoebus dims the lights," says the princess, lifting her goldrimmed wine glass and collecting eyes. "That's Homer. No, these glasses are not from the Imperial Yacht but those just over there are. Did Andrew tell you that we found Catherine the Great's teapot in an antique shop in Soho with a price of 3 pound 10 on it?"

Provender, as the Romanoffs call it, looks like the stage set for a medieval castle. It was built in 1246 and the scale is very grand. The walls are either paneled or covered with scarlet flocked wallpaper and the fireplaces in every room soar to the ceiling. The Romanoffs turn off the heat June 1, which is not necessarily when Kent warms up, and have to huddle about wood fires to keep reasonably comfortable.

The Romanoff food is wonderful. The princess attended a cooking school along with Lady Mountbatten, and though the kitchen is staffed, the servants only stand and serve. The prince often cooks the meat and he painted the design on the mats used on the table.

The conversation is always breathtaking.

"I pray every night for Raaputin," says the princess, cutting into her lamb. "He didn't take a bath, and he drank, and he boasted of his friendship with the emperor, but he was not evil. He had the power to heal hemophilia. He was the living serum. You know he said if anything happened to him, it would be the beginning of Russia's downfall."

The prince looks up from his plate. Talk of hemophilia troubles him, but the princess is off again, this time on a story of how the empress' pearls were so large that when the Bolsheviks searched her room and found them, they thought they were fake and left them behind.

The luncheon is elaborate because of the visitors.The princess herself is a disciple of Gaylord Hauser, has drunk in every word he ever wrote, keeps his books beside her bed and swears by his recommmendations. She is determined to get down to 126 pounds because she has a gorgeous dress she will then fit into. Dessert is rhubarb because Hauser recommends it.

After lunch she plays a few chords of the Russian Bells of Moscow and, losing interest, sweeps her guests into the drawing room to see the Faberge eggs, the Bellini madonna, the Medici cabinet and her own enormous dried flower arrangements.

The prince watches it all quietly from the sofa, sipping his coffee, occasionally erupting into the loud preliminary throat clearings which mean he is about to speak.

"It wasn't the Crimea," he will say mildly to his wife, or, stirring his coffee morosely, "Why is all London turning out for that Romania communist?"

Among the first visitors to partake of the Romanoff hospitality was a group of vacationers from Houston who came over on the Concorde and were staying at Claridge's when the hall porter suggested a trip to Provender. The princess fell in love with them at first sight and was quite determined for a while to limit her American guest list to Houstonians.

"The darlings," she murmurs, looking back fondly, "we couldn't get their hats from them.I finally persuaded them to put them under their chairs when we ate."

The Texans loved everything, from the cold pheasant to the before-lunch, specially concocted punch. When they took their leave, the princess noticed them conferring in a huddle in the corner of the room.

They had been trying to get up nerve to ask her if they could take along the rest of the punch in a thermos for the bus.

"It's quite a long way to Claridge's," they said, "and we might get thirsty."

The princess was enchanted with such forethought and packed them off fortified for the trip.

Her current ambition is to visit Houston. CAPTION: Picture, Prince and Princess Andrew Romanoff outside Provender, their home in Kent, which once belonged to England's Black Prince Edward. By Elizabeth Mooney for The Washington Post