As one of a small group ITK, I heard that Prince Philip ordered them to cease production.
As an aside they also filmed at least one scene in Nipper Alley, Kingston (where Nipper the HMV dog lived) and they also used a rather ugly concrete housing estate in Swiss Cottage for a lot of scenes. The same housing estate was used in the very recent BBC dramatisation of The Little Drummer Girl.
That Alley is now used primarily as a smoking area for one of the worst 'spoons in the UK. Utter hole. Sad really.