Office handover and handshake sets in motion UK's departure from European Union

A bitter, divisive campaign and 33 million votes later, Brexit came down to two men and an envelope in a smart Brussels office.

Last year's referendum had passionate debate and hard fought campaigns, leading to the historic decision that Britain should leave the European Union.

But for all the excitement of a big red bus, high profile poster campaigns and street stalls across the country, the actual mechanics of starting Brexit were a lot more mundane.

Sir Tim Barrow, only three months into the job as permanent representative of the UK to the EU entered the room of European Council president Donald Tusk armed with a white envelope.

The pair spoke in hushed tones surrounded by two Union Flags and two European Union flags in a room on the 11th floor of the Europa building.

Then, as cameras rapidly fired away to capture the historic moment, Sir Tim passed the letter to Mr Tusk, confirming the intended departure.

The pair shook hands and left, Mr Tusk to an office on the left and Sir Tim down a corridor to the right.

The formal triggering of Article 50 had begun and the UK was officially on a course to leave the European Union after 44 years.

It was not the bang of June 24 last year, David Cameron's resignation, Nigel Farage holding a pint aloft, Scotland seeking a new independence referendum but not quite a whimper either, as the future relationship between the UK and the EU looks set to change for good.