The Corvini Inheritance (1984)
Part of the 13 episode television series, Hammer House of Mystery and Suspense.
Frank Lane is obsessed with surveillance, which is his business and his leisure occupation. When his neighbour is pestered by a stalker, Lane is in the ideal position to instal the necessary preventative measures. His equipment finally captures the threatening figure on video as his neighbour's flat in broken into as part of a violent assault. As the monitors play to an empty room, we see the obsessed face of Lane himself as he breaks in.