Tristram begins walking north, and as he passes through the city, he notices more than one pair of men and women openly having sex in the streets.
Tristram passes by a Mass being given out in the open air, and notices that the priest is handing out rounds of meat rather than communion wafers.
Outside of Barnet, Tristram manages to hitch a ride with a van heading towards Aylesbury. As they drive, the driver of the van tells Tristram that he needn't have bothered escaping from prison: that morning, all prisoners had been released.
The van's driver gets Tristram up to speed on other changes he's missed since being in prison, and tells him that the central government has collapsed. He also tells him that food factories have begun canning human flesh, and calling it "tinned pork" (4.2.11).
Evidently, new lines are being drawn between "civilized" and "uncivilized" kinds of cannibalism. As the driver of the van tells Tristram, "[i]t makes all the difference if you get it out of a tin" (4.2.17).