The memory lingers

In that living, changing theater that is London, a certain few figures from the past demand center stage. One can readily see Dickens here and there, and Queen Victoria and Christopher Wren are highly visible, but perhaps no one plays a more pervasive role than Winston Spencer Churchill. For me, Winnie is everywhere.

Churchill will be gone 20 years next January, and later in 1985 it will be 40 years since he saw Britain through the end of World War II. Yet even today it is not hard to conjure up the image of the ever-hopeful prime minister striding through the bomb-torn city, raising two fingers for victory. For more tangible evidence there are busts or statues at St. Paul's, Parliament Square, and Guildhall, but perhaps the most novel memorial is an underground warren of rooms on Great George Street near Whitehall.

These are the Cabinet War Rooms, used as a hideaway by Churchill, his war Cabinet, and the chiefs of staff during the bleakest days of the war. In 1981 the rooms, scarcely altered from their wartime use, were turned into a museum, and a well-done one at that. On sunny days when half the world seems to be thronging the Tower of London, Westminster Abbey, and Madame Tussaud's, this subterranean retreat is orderly and quiet.

One needs the resourcefulness of a secret agent or at least the pluck of a seasoned tourist to find the museum. Having consulted at least two bobbies, I finally found the hidden steps and soon was 10 feet below the pavement and heading back 45 years in time. The Cabinet War Rooms are the surviving and most significant part of underground emergency accommodations the British threw up to protect their leaders in the threatening days just before the war. The hideout was chosen for its proximity to Whitehall and for the extra security offered by the steel-framed structure of the building above.

Starting along the maze of narrow corridors, one comes first to the Cabinet Room, which was used 100 times by Churchill, his war Cabinet, and defense committee between 1940 and 1945. They were driven underground most frequently during the blitz of September-November 1940 and four years later when the Germans raked London with a V-rocket offensive.

You look through a glass panel at a room arranged to look as it did for a meeting on Oct. 15, 1940, at the worst of the blitz. A clock on the wall reads a few minutes to 5. At the center of the 30-by-30-foot room is a horseshoe-shape table covered with somber navy blue cloth. Around it are 23 chairs, including a wooden swivel chair favored by Churchill, who sat before a large pull-down map of the world. There are electric fans in each corner, and above the door are two small electric bulbs, one red and one green, to indicate whether an air raid was in progress.

Along the main corridor you pass a hatchway leading to a subbasement where many of the staff slept during the worst bombing raids; a mess room; and a weather board, which was occasionally marked ''windy'' during air raids - a joke to keep spirits buoyed.

One of the most vital chambers is a phone room Churchill used to speak directly to President Roosevelt in the White House. On a desk beside a green-shaded lamp are the earphones Churchill used for those conversations. Throughout the war, devices called scramblers were used to transform conversations into meaningless noise; then the words were unscrambled on the other end. An airtight link did not exist between this room and Washington until mid-1943, when the Bell Laboratories developed an advanced scrambler. It was too large for the Cabinet War Rooms, though, and had to be installed in the basement of Selfridge's department store on Oxford Street and connected to the phone room by underground cable. I had to chuckle at the thought of all the meaningless noise going on at that very moment in Selfridge's basement, at the peak of London's July sales.

As I passed a series of rooms, each equipped with typewriters, desks, sleeping cots, and World War I iron helmets hung on wooden posts, I found myself listening to the comments of an English threesome - presumably grandmother, daughter, and granddaughter. ''Sugar was rationed in those days,'' said the grandmother, ''and I remember we could only get 31/2 bottles of milk a week.''

''Goodness, we have 18 delivered now,'' said the mother. Added the eldest: ''And we could buy a half leg of lamb once every fortnight.'' The youngest, perhaps 10, merely gazed on the displays.

In the Map Room you see the very wall maps used at the end of the war, with a series of pins showing the movements of convoys and individual warships. Churchill's private room is next to the Map Room, furnished with a cot covered with a greenish quilt, a floor heater, and a large map of the area between London and the Suez, partly concealed by half-drawn curtains. Churchill slept here only three times during the blitz - he found the toilet facilities inadequate - and after December 1940 he and Mrs. Churchill lived in private apartments upstairs on the ground floor. He did make a number of telling broadcasts from the dungeon room in 1940 - an invasion warning on Sept. 11, a broadcast to the French on Oct. 21.

I tracked the Churchill presence elsewhere in London, realizing that one cannot enter St. Paul's, for example, which he ordered preserved through the bombing, without recalling his - and the church's - indomitable wartime spirit. My favorite memorial, though, is the Churchill Room of the Jermyn Street shirtmakers, Turnbull & Asser. Churchill was a longtime customer, and in a glass cabinet resides a green velvet siren suit he wore in the war rooms. Even in the darkest hours, Sir Winston went in style.