Prince Harry -- Reunited With Beloved Teacher ... 17 Years After Diana's Death

Prince Harry just experienced how small the world really is ... because today he ran into his former teacher who consoled him during Princess Diana's tragic death.

The Prince got a huge shock while greeting an ecstatic crowd in Christchurch, NZ -- Vicki McBratney stepped forward and brought an unexpected smile to Harry's face. McBratney was by his side at London's Ludgrove School in 1997 as he dealt with the horrific news.

They shared a brief hug, friendly kiss on the cheek, and she handed him childhood pics from his school days -- and it's obvious they were close.

Cool moment for Harry.