V stops a train carrying Prothero and kidnaps him. He is driven insane by a combination of an overdose of Batch 5 drugs and the shock of seeing his prized doll collection burned in a mock recreation of Camp Larkhill in V's headquarters. He remains incapacitated for the rest.
In the film, he is portrayed by Roger Allam. Here, his identity is publicly known, and he serves as "The Voice of London", delivering Party rhetoric to citizens.
Unlike the graphic novel, the film Prothero is killed in his shower by V.