Watching The Zygon Invasion reminded me that Paul Cornell once wrote that the Third Doctor in a Prisoner-Of-War camp would be 'sour'. Yet he also argued that the Seventh Doctor in that environment would not be. His reasoning, I guess, was that no writer could sustain something as artificial a construct as the Third Doctor - with his 'mother hen' and UNIT family and going cross-eyed when in danger - within a setting as real, visceral and sensitive as a pogrom.
In The New Adventures - a series that contained racism, sex, swearing and everything in between - the tone could support a deeper, darker level of material. I may not agree with Cornell, but I can see the point. There has to be an envelope in which the series exists - push too far in different directions at the same time and the whole thing becomes uneven, uncomfortable, perhaps inadvisable. Sour.
Yet in The Zygon Invasion we got precisely that: the nightmare scenario. A Doctor that plays his own theme tune on an electric guitar one week; plays hide and seek with a character out of a two Ronnies sketch another and in the next he battles terrorists who converse in the same language and medium of people who are - right now - slitting the throats of people they judge to be different from themselves.
A story that has our hero advising a UNIT commander that her troops should 'try not to kill all of them' and has Kate Stewart surveying industrial bins full of human bodies. In a series whose tone isn't wildly out of kilter with the stuff you can see on CBeebies and also contains references to Isis execution videos. It's a show that can wave around words like 'radicalisation' and 'funkenstein' within minutes of each other.
The general irrelevance of the Doctor to the plot was instructive. Instead we got people designed to be relatable, believable, because in the world of The Zygon Invasion the Doctor strikes a sour note. We cannot ever square the man from The Daemons, City of Death, The Five Doctors, Time and the Rani, New Earth, The Crimson Horror with this Doctor.
That's what Paul Cornell was talking about: he was wrong to say that solely the Third Doctor - played by a man, lest we forget, who served in WWII - could not enter into certain fictional spaces. But he was, I think, right to suggest the Doctor cannot and should not move in some fictional spaces because whatever happens the show will always have a high level of absurdity.
It's always been there in the series' texture; in recent years the childishness of Doctor Who has been ramped up to 11. When it's mixed with the kind of gruesomeness we saw in Dark Water or an atrocity allegory the whole concoction curdles.
What we saw in The Zygon Invasion was Doctor Who Meets The Taliban; An Exciting Adventure With Muslim Extremists. Despite the direction, acting and even Murray Gold managing to keep a lid on his usual histrionics, we had something that some people sensed was... wrong. Sour.
Steven Moffat may believe Doctor Who has moved beyond tone. To me The Zygon Invasion was evidence of a programme that has slipped its moorings. It no longer knows what it is or who it is for.
Doctor Who now operates on a level of its own. It's setting its own rules. A programme that simultaneously mines the depths of day-glo stupidity and visceral everyday horror. The Zygon Invasion demonstrates that it no longer operates as parody nor pastiche. In modern Doctor Who the only question is 'should we go there?' and the answer is always 'yes'.
Watch it here on iPlayer