Andrea, 39, a Londoner, is an occupational psychologist who used to advise companies on how far a prospective employee was likely to fit in, from the point of view of personality, values and behaviour under pressure. She said: 'I was watching a Kilroy show one day, and the discussion was about children who are mistreated or even killed by their nannies or the au pair, when a woman in the audience said 'We know all about a nanny's references and CVs but how much do we know about the personality behind them?'