A synonym for invigilate is proctor. Its root or stem is vigil which is purposeful sleeplessness or wakefulness. One of Richard Dawkin’s minor functions at Oxford was that of an invigilator or an exam proctor.
Dawkins relates a story about an invigilator for a psychology tutor named David McFarland where the proctor informed the tutor that a particular examinee’s hand writing was getting larger and larger attributable either to a nervous breakdown OR an attempt to cheat by making his answers more visible to that special someone nearby.
If these type of accounts intrigue you, you must read more output from The Blind Watchmaker’s author. His quite non-chronological effort titled Brief Candle in the Dark was the origin of this snippet.
Yes, he chose not to employ definite or indefinite articles to precede Brief in title. A Brief ….. would be not distinguishing enough. The Brief ….. would be too arrogant and egotistical.