Should your head trump your heart when seeking lifelong love? That's the challenge Business Daily's Justin Rowlatt has taken on for this Valentine's Day. The hyper-rationalist businessman Ed Conard thinks he knows the answer, and his strictly mathematical strategy for romance is called "sequential selection, no turning back". He used it to meet his wife of the last 20 years, Jill Davis. But is Ed's approach right for everyone? Justin hears sceptical voices from two very different quarters - romantic novelist Nicola Cornick, and Nobel prize-winning economist Alvin Roth. And what about Jill? What's it like to be on the receiving end of such a calculated courtship? (Picture: Jill Davis and Ed Conard; Credit: Patrick McMullan via Getty Images)