After the second task, Fleur tracks down Harry to thank him for saving her sister. They end up talking until late in the night, at which point they go to the kitchens for a bite. Fleur also convinces the House Elves to part with a bottle of red wine. So at like 3 am, they are tired, tipsy and comfortable on a couch Dobby had organised them. The talk turns to relationships, and Harry gets a bit melodramatic, Fleur replies in kind and it becomes a "who has it worse" pissing contest, which ends with a "if we're not married by 20, were getting married to each other" deal. Originally, they started with age 40, but because of the "hardships" they face, they negotiated each other down (being a Veela, being famous, fangirls, allure). Fast forward to Harry's twentieth birthday when he receives an unexpected letter from the Delacour solicitor about a contract he entered in 5 and a half years ago...