Postwar. Harry invited his neighbour Fleur on a cup of tea to a nearby Café, where something truly ridiculous happens (bank job, attempted terrorist attack, cartoon-y supervillain with a ridiculous device, a parade displaying 150 years of emergency sirens).
So after dealing with whatever crisis, they reschedule for next week, only for another ridiculous thing to interrupt, and again the week after... So rather than getting that date, they bond over making it through all those ridiculous things.