Editor’s Note: Nic Robertson is CNN’s international diplomatic editor. The opinions in this article belong to the author.

There are times when working as a journalist provides a front-row seat to some of the most important events taking place on Earth. On the downhill slope to Brexit, Derry – also known as Londonderry – certainly fits the bill.

Since the end of The Troubles, Derry has become a vibrant cultural hub. It hosts Europe’s largest and most vibrant Halloween celebration each year, attracting thousands of tourists. It was designated the UK’s City of Culture in 2013.

But a car bomb last weekend that blasted granite chunks off the street and through windows lifted the curtain on something darker going on in this city on the border with the Republic of Ireland.

It revealed an unholy mess that has gone unnoticed by too many for too long. As they say in Derry, even the dogs in the streets know. So why don’t the politicians who sit in London?