'Fill it up, guv?' -- 'No, plug it in please'

Ignition: on. . . . Parking brake: off. . . . Noise: none. . . . Shift lever: missing. Depress the accelerator, however, and the tiny Enfield electric prototype, its back seat full of wires and circuitry, rolls to life. Soon we are humming busily along through traffic -- quietly, odorlessly, and feeling terribly virtuous about all the gasoline we're not using.

With predictions that the world's oil valves will be turning off in the next few decades, a number of far-from-wacky businessmen here are getting switched on about the future of the electric automobile.

Britain, generally acknowledged as a world leader in electric-vehicle sales and design, already has some 40,000 on the road -- mostly "milk floats" used for doorstep daily deliveries.

Now, however, a load of high-powered current is flowing to solve a single problem: how to design a vehicle that meets the public's demand for performance and range, yet falls within acceptable costs. Experts foresee solutions by the mid-1980s.

"Cost is absolutely the essence of the whole thing," says Dr. Brian Edwards of Chloride Technical, Ltd., the battery manufacturers. For him, the electric is an idea whose time has come, gone, and come again -- all because of cost. In 1899 an electric car held the world land-speed record of 66 m.p.h. And until about 1910, electrics out-numbered their gas-eating cousins. Then cheap oil drove them out of the market.

Now there is hope once more. Diesel fuel prices increased 55 percent last year. Electrical component prices and weights are falling, and new technology hints at lighter and more efficient nickel-zinc or sodium sulphur batteries. Environmental arguments are also getting charged up.

Chloride already markets a two-ton Dodge van, modified on the production line to take 80 lead-acid batteries. With a top speed of 40 m.p.h. and a range of only about 50 miles between charges, it won't dazzle Mario Andretti. So far it has only proved practical for laundries and postal services.

Price is still a problem: Over an eight-year period, the initial expense more than offsets the 25 percent reduction in maintenance (due to low vibration and fewer moving parts) and the 66 percent saving in fuel costs. Nevertheless, Chloride is willing to subsidize the costs, hoping to generate a market and spur research.

Geoffrey Harding of Lucas Industries agrees that cost is the challenge. Midway into a three-year, L6.5 million ($14.8 million) research program, he has let loose 65 modified Bedford vans on London, each with a ton of batteries and a promise of constant maintenance and testing.

However, "if you converted every one-ton van in the world to electric drive, you would not save much fossil fuel," Mr. Harding says.

Next target: the passenger car. "You can't do it with the lead-acid battery, " Mr. Edwards says. A compromise may be a hybrid car, driven by an electric motor energized both by batteries and by a diesel-powered generator. Dragonfly Research, a division of Lee-Dickens, is working on a sleek two-seater.

But so far no one talking cars will talk prices. The aim is to bring them down to about 10 to 50 percent above normal automobile prices.

The highly political nature of oil and electricity tariffs cloud the future somewhat. Except, that is, for enthusiasts like violinist Yehudi Menuhin, who rides an electric bicycle. And Prince Philip, who reportedly wants an electric car for Buckingham Palace. With them leading, others may follow.