The Runaway, by Martina Cole

When Cathy Connor and Eamonn Docherty are thrown together as children in the East End their fate is sealed. Cathy's miserable life as a p_ostitute's child changes forever when she's forced into care. The ordeal that follows leaves her with no choice but to run away to Soho, and she learns to survive in the violent heart of London's underworld. Meanwhile, Eamonn, who fled to New York, has gained a reputation as a ruthless villain. But when their paths cross again, Cathy's an equal match for Eamonn.