Diana had accelerated up to fifty again when she suddenly became aware of a pair of headlights shining through her rear windshield. She put up her arm and waved in her rearview mirror, but the lights continued to dazzle her. She slowed down to allow the vehicle to pass, but the driver showed no interest in doing so. Diana began to wonder if there was something wrong with her car. Was one of her lights not working? Was the exhaust billowing smoke? Was…?

She decided to speed up and put some distance between herself and the vehicle behind, but it remained within a few yards of her bumper. She tried to snatch a look at the driver in her rearview mirror, but it was hard to see much in the harshness of the lights. As her eyes became more accustomed to the glare, she could make out the silhouette of a large black van bearing down on her, and what looked like a young man behind the wheel. He seemed to be waving at her.

Diana slowed down again as she approached the next traffic circle, giving him every chance to overtake her in the outside lane, but once again he didn’t take the opportunity and just sat on her bumper, his headlights still undimmed. She waited for a small gap in the traffic coming from her right. When one appeared she slammed her foot on the accelerator, shot across the roundabout, and sped on up the A1.

She was rid of him at last. She was just beginning to relax and to think about Sophie, who always waited up so that she could read to her, when suddenly those high headlights were glaring through her rear windshield and blinding her once again. If anything, they were even closer to her than before.

She slowed down, he slowed down. She accelerated, he accelerated. She tried to think what she could do next, and began waving frantically at passing motorists as they sped by, but they remained oblivious to her predicament. She tried to think of other ways she might alert someone, and suddenly recalled that when she had joined the board of the company they had suggested she have a car phone installed. Diana had decided it could wait until the car went in for its next service, which should have been two weeks ago.

She brushed her hand across her forehead and removed a film of perspiration, thought for a moment, then maneuvered her car into the fast lane. The van swung across after her and hovered so close to her bumper that she became fearful that if she so much as touched her brakes she might unwittingly cause an enormous pile-up.

Diana took the car up to ninety, but the van wouldn’t be shaken off. She pushed her foot further down on the accelerator and touched a hundred, but it still remained less than a car’s length behind.