Z-Cars

Z-Cars was a BBC television series that ran from 1962 to 1978. It centred on the work of mobile uniformed police in the fictional town of Newtown.

In 1965, it was hoped by the production team of The Daleks' Master Plan that they could use the Z-Cars set and some of the regular cast for the scenes of "The Feast of Steven" set in a police station. However, David Rose, the producer of Z-Cars, withheld his permission for this. (REF: The First Doctor Handbook) This was alluded to in the novelisation of this episode, in which the policemen (unnamed in the televised story) were given the names of some of the Z-Cars regular cast. (This would've been Doctor Who's first crossover with another series or franchise. The first actual crossover was in Remembrance of the Daleks with its allusion to Bernard Quatermass.)

As with Doctor Who, many episodes of Z-Cars were wiped from the records by the BBC once they were believed no longer useful. During the search for missing episodes of Who, several Z-Cars episodes were also found. (DOC: The Missing Years)