She doesn't restrict her filming to her own classroom. Rightly or wrongly, she is convinced that the school hierarchy has it in for her and that she may fall victim to the next round of redundancies. So she is preparing her counter-attack by compiling video evidence of the management's incompetence.
She is, for example, recording examples of the school's top earners turning a blind eye when they pass misbehaving pupils, of classes left unattended while meetings drag on, of the deputy's car racing out of school long before the last bell, and of various other indiscretions that would prove rather embarrassing were they to be shown to Ofsted inspectors, parents or - in some cases - spouses.
Should senior management as much as hint that her contract is under discussion, she intends to invite them to a private viewing. She is quietly confident that this should help them arrive at the right decision.
I met my pleasantly paranoid informant during the interval in the WNO's production of Benjamin Britten's Billy Budd. She was surprised that I hadn't been struck by the uncanny parallels between the regime on an 18th-century warship and that of a typical state school.
The officers on HMS Indomitable are exclusively male. They are arrogant, dictatorial, petty, woefully ill-informed and treat the other ranks with undisguised contempt. Because Billy - brimful of idealism, courage and youthful ambition - refuses to kowtow to one of his superiors, he is victimised and ultimately destroyed. The opera, she insists, should be a compulsory element in every teacher training course.
Her worried husband apologised. He explained that, probably because she was working too hard, she couldn't help but find echoes of her school in everything that they ever went to see. He warned me not to ask her what she thought of Titanic.
As Billy Budd exemplifies, in the days when Britain ruled the waves, the Royal Navy, despite its many shortcomings, had an effective way of dealing with recruitment - one that the Teacher Training Agency must secretly envy. The Admiralty didn't ask the likes of actress Miss Sarah Siddons or Dr Samuel Johnson to appear before the sceptical public eulogising "my best sailor" in the hope that it would lure impressionable lads into the Senior Service. The use of press gangs rendered such advertising unnecessary.
I don't suppose this government will ever empower the TTA to lurk in dark alleys at closing time, ready to pounce on unsuspecting graduates. However, they could always be reminded of Billy's fate. And to ensure that message hit home, the money saved by abandoning the TTA's wasteful advertising campaigns could be spent on giving every state school a gang plank.