A showman brings the past to life in restored Georgian mansion

As the electric lights are going out at the Bank of England, the candles are being lit at Dennis Severs's house a short distance away. The night descends, his fires are kindled, and the atmosphere is now right for the evening's small group of visitors.

His house, built in 1725, is just to the east of the City of London and is in an area known as Spitalfields, where prosperity has come and gone with the rise and fall of the silk weaving industry. Today the area teems with markets and workshops mostly in the rag trade, but unemployment and terrible poverty have colored the look of the place for 150 years, ever since the time when the silk industry first began to decline.

But Spitalfields is now in the early stages of rehabilitating its wealth of Georgian buildings. And at the heart of the area and with a fruit and vegetable market at the back door is the house of Mr. Severs. From the outside, the house appears to be somewhat unprepossessing. But once one is inside, that impression is forgotten.

Immediately on entrance, he is beckoned into a dim, narrow hallway and then led by candlelight down a servants' stairway into a cellar back room. A candle flickers for company as the other visitors are awaited. Whispers seem appropriate in this somber room until the mood is enlivened with the appearance of Mr. Severs.

Having for nine years run a horse-drawn carriage tour through Kensington and Chelsea, pointing out historical details as though he personally lived through the 19th century, the American-born Severs is used to sharing his own intimate sense of history. He has a vivid understanding of how the past was lived; and also, of equal importance, he is a showman. He knows how to make things that might seem dull, pure entertainment. He chose to live in England because of a fascination with its history, and now he chooses to live and illustrate to others exactly how that history was lived by ordinary people.

The house selected for his purposes was a derelict Georgian building, untouched since World War II. He stripped the house of most of its electricity in order to use only candles, oil lamps, and open fires; he uncovered original paneling underneath wallpaper and plasterboard; he faked molding and paneling where there were none; and he made glazing bars for the Georgian windows out of twigs and putty. Although the result is authentic in appearance, shortcuts had to be taken in the restoration. But for a mere (STR)400 (about $960) and in only six months, Severs has created something that is entirely magical.

Before he takes his visitors around the house, he first tells the story of Spitalfields and how it was settled by the Huguenot silk weavers who sought refuge from persecution in France. He outlines the history of the silk industry and describes the poverty of the area after the industry's collapse. The picture is drawn with great clarity; indeed, ''the tour,'' says Severs, ''is about a collection of atmospheres.''

But the focal point is the house and its story, told through the experiences of the fictitious Jervis family, who lived and worked in the house for several generations. What the visitor is about to see are rooms that reflect not only the times and trends of each period, but rooms seen through the eyes and needs of the Jervis family.

''You can take the house of, say, a doctor or a lawyer,'' Severs says, ''and play the same game I have with the silk weavers. The idea is that these were not great people who affected history, but history affected them. I used the Jervis family as a device for ordinary people to see how other ordinary people lived through four generations.''

Beginning with Isaac Jervis, a Huguenot who in 1685 smuggled himself out of France in a wine cask, one is told of his success, his respected position as a master silk weaver, and his move into this new Georgian house of 1725.

From here, one is taken on an excursion through the house, each room from a different period, each period a different generation of the Jervis family. One sees the house reflecting the Jervis prosperity and the house when the silk industry sinks.

With Mr. Severs leading the way by candlelight, one goes up and down several flights of stairs and enters each room to sound effects appropriate to the room's period. Events of the time are related as though they were contemporary. In several rooms, portraits of the Jervis family make their presence all the more believable. One is shown the dining room, the kitchen, bedrooms, and the drawing room and smoking closet, and the tour ends in the cozy Victorian morning room. Only the kitchen remains untouched by time, ''because,'' Severs explains, ''it was never seen by anyone other than the servants.''

On the first floor one is in for a breathtaking surprise: the drawing room. A warmly elegant room of dark paneling, ''family'' portraits and walls festooned in the manner of Grinling Gibbons, this is, in the purest sense, a drawing room. Here, according to Mr. Severs, the ladies withdrew to sit in grand wing chairs, chatting of gowns and the latest gossip. And next door, the gentlemen retired to the smoking closet to talk of politics before a large open fire. Eventually the men would join the ladies and then gracefully parade up and down the center of the drawing room, showing off their costly silk attire.

''You begin,'' says Severs, ''to get an idea of how rooms were used and why certain things were bought.'' Even now, after the house has been exquisitely completed, Mr. Severs continues to acquire things. ''But when I shop,'' he says, ''I ask myself, would Mrs. Jervis like this?'' Taking this one step further he adds, ''After people leave the house, a few might just wonder when they see or hear about the 18th century, what would the Jervis family have been doing then?''

For information about the tours: Dennis Severs, 18 Folgate Street, London, E. 1 Tel. 247-4013. The tour costs (STR)10 per person for 2 hours.