Sheer abandon

One night in 1986 an abandoned baby girl is found in a cupboard at Heathrow airport. A year earlier Martha, Clio and Jocasta had met by chance, at the start of a backpacking they travelled together briefly and then went their own ways, swearing to meet again when they return home. But it would be a long time until they met not until Kate, the foundling, is a teenager, and all three are leading successful lives. Martha is a single, highly paid lawyer, Clio a doctor, locked in an unhappy marriage, and Jocasta a reporter, in love with a charming commitment-phobe. Which of them is Kate's mother? Why was she desperate enough to do such a thing, and how did she survive it? [goodreads.com]