Penny Jordan, an author writing for Mills & Boon, has stated that "[the rules] are not written down, but if you diverge from reader expectations, they won't read your second book." In popular imagination and feminist criticism, the heroine of a stereotypical Mills & Boon novel is often seen as a passive virgin who is submissive to the hero in every way. This was often true in older novels but changed over the years; modern novels feature more active protagonists. Mills & Boon heroines cover a wide variety of types, often depending on the author's preference. Romantic encounters were embodied in a principle of sexual purity that demonstrated not only social conservatism, but also how heroines could control their personal autonomy. The attributes of the heroes of Mills & Boon novels have not significantly changed over time, however, almost always being a dominant alpha male. Joanna Bowring, co-curator of the Mills & Boon centenary exhibition at Manchester Central Library in 2008, notes that "there's always been a subtle undercurrent of force throughout the books and that's never changed from the earliest ones. Even later, when other aspects are influenced by feminism and the shifting attitudes outside the novel, the men are masterful and stern." In 1966, the Mills & Boon author Hilary Wilde said "The odd thing is that if I met one of my heroes, I would probably bash him over the head with an empty whisky bottle. It is a type I loathe and detest. I imagine in all women, deep down inside us, is a primitive desire to be arrogantly bullied." Many critics point to the comments by another of Mills & Boon's writers, Violet Winspear, in 1970, that all her heroes "must frighten and fascinate. They must be the sort of men who are capable of rape". Bindel argues that, as heroines have acquired greater agency, the heroes have become even more domineering and misogynistic. Other critics contend that these characters are outdated and inappropriate for modern works. However, supporters of the publisher counter that Mills & Boon are careful to follow their readers' tastes and interests; if the hero follows this trend it is because that is what the readers want. In modern novels, popular hero archetypes are Arab sheikhs, Italian billionaires, Greek tycoons, and princes. According to Mills & Boon author Sharon Kendrick, "the sheikh represents the ultimate female fantasy." Penny Jordan adds that