Who is Dexter Mayhew from One Day and what is their importance?

Dexter Mayhew is one of the two main characters in the novel "One Day" by David Nicholls. Dexter is the son of Alison and Stephen Mayhew, and is from a family of wealth. Dexter is thin and handsome when the novel begins, and has an appetite for girls and for fame. He has a one-night stand with Emma Morley while at university in Edinburgh, unaware that the encounter will change the rest of his life.