Observation is the 331st episode of The Bill.
D.C.I. Reid takes over a joint surveillance operation with the Flying Squad. D.I. Burnside and W.D.C. Martella are asked to leave the flat they are observing from by the drunken tenant, who then beats his wife. When he comes into the street after her, looking as if he'll blow the operation, Burnside arrests him (by throwing him face-first against a lamppost).