Even in death, Mandela showed his power to unite people. This was quite an extraordinary moment between the two nations, hostile for half a century. Barack Obama did not just given Raul Castro a quick handshake, but bent down and spoke briefly to him.
Obama spoke a few moments later of "Ubuntu", which he called Mandela's "greatest gift: his recognition that we are all bound together in ways that can be invisible to the eye; that there is a oneness to humanity; that we achieve ourselves by sharing ourselves with others, and caring for those around us."
Something he perhaps had in mind as he approached Cuba's president.