For London the worst has happened. There have been riots, huge uncontrolled fires, outbreaks of savage looting, artillery battles, mass flights. The great city lies three parts deserted, open to marauding gangs and beast-wild individuals, its highways and landmarks tumbled like ruined temples.

To Mark, comparatively safe up in less troubled Highgate, there comes a message that his estranged wife is dying over in Wimbledon, right across on the far side of the dangerous bowl of the devastated city. Reluctant almost to sticking-point, he sets out to go to her.

His journey is a story of adventure through the ruins. His immediate business is the simple one of pressing on through all the debris, always driven because he knows that Jasmine will die soon. He may never get there: he may be killed by idiotic accident, torn to pieces by the packs of wild dogs, trapped in one of the communes that within their stockades have established their own ruthlessly puritanical disciplines.

But the difficulties and the dangers teach him lessons as he struggles onwards. He learns from the past. If it was drink, drugs and the dolce vita that had done for his wife, had not something similar destroyed the city too? He learns about the present amid its hazards. And he learns, as he comes at last to the bleak end of his Iong walk, lessons for a just possible future.