Flowers from the Storm by Laura Kinsale

The Duke of Jervaulx was brilliant and dangerous. Considered dissolute, reckless, and extravagant, he was transparently referred to as the ′D of J′ in scandal sheets, where he and his various exploits featured with frequency. But sometimes the most womanising rake can be irresistible, and even his most casual attentions fascinated the sheltered Maddy Timms, quiet daughter of a simple mathematician.