I used to presume that these busts would be from chaps / chapesses who are less familiar with the area around London (the Dutch pilots cited in the list for example) and that people like us who have trained in, under or very near to the TMA at Wycombe, Denham, Waltham, Elstree, Biggin, etc would be less likely to be the culprits as we have it drummed into us hard from an early stage... but there are also several apparently local examples (e.g. out of Waltham) cited, which probably blows my theory!
Vigilence and Preparation!
Andy