Each day in the central lobby of the Palace of Westminster, one that separates the House of Lords and the House of Commons, visitors crane upwards to see four mosaics.

Representing Saints Andrew, George, David and Patrick, the mosaics have browned with age and few will have noticed the name of Banba written above the head of St Patrick.

For Dan Mulhall, Ireland's ambassador to Britain, however, the presence of Banba – a member of the legendary Tuatha Dé Danann – highlights the complex heart of Anglo-Irish relations.

Fifteen years ago, Mulhall was based in Edinburgh, as it made its first steps after the devolution of power to Holyrood from Westminster.

There, he became friends with the late Seamus Heaney, agreeing with the latter’s view that the two countries were “linked and separated in various degrees by history and geography, language and culture”.

“Considering our convoluted connections, it seems strangely appropriate that this ancient Irish goddess should occupy this perch,” Mulhall mused recently.

For months, the Waterford-born diplomat has led preparations, at the Irish Embassy in London, for President Michael D Higgins’ State visit to Britain.

Often, it has been a job of explaining – to a British audience or to those internationals who have become intrigued – why the first State visit by an Irish head of State is only taking place now.

“For a long time relations between an independent Ireland and our nearest neighbour were burdened by a legacy of history,” he told journalists last week.

The four-day programme will reflect the “huge divide” that has been overcome in relations between Ireland and Britain, but one also that offers “a platform for the future”, he said.

During the visit, Mr Higgins will lay a wreath at the Tomb of the Unknown Warrior at Westminster Abbey and inspect the colours of the Irish regiments disbanded when the Free State was founded.

“In the past we might not have seen that Ireland had any real connection with the first World War,” says Mulhall, noting the series of commemorations involving Irish ministers in recent years.

“It underlines our willingness yet again to see our past in its true colours and embrace our past without any reason to shy away from the fact that the Irish played such an important role,” he went on.

Since he moved to London from Berlin last year, Mulhall has spent time getting to know the Irish community, particularly those involved in a succession of Irish centres throughout Britain.

Last month, 350 Irish people were invited to Buckingham Palace for a reception that acted as the warm-up to President Higgins’ visit– one that is getting royal attention.

“It is a wonderful occasion for the Irish community in Britain; the biggest Irish community anywhere in the world outside Ireland,” said the diplomat on the night.

“They have made a huge contribution to Britain over the years. Many of the people here tonight have been here for 40, 50 or even 60 years,” he said.

The ties that bind are cultural too, says Mulhall, pointing to Mr Higgins’ visit to the Royal Shakespeare Company in Straford-upon-Avon and, later, Shakespeare’s birthplace.

“For the Irish, Shakespeare hardly counts as a foreign author; he has been part of our lives. Equally, here, people regard Irish authors as part of their own literary tradition,” he said.

Prone to quoting Heaney, Mulhall wondered, in a speech in Edinburgh some months ago, if Banba “was the goddess” the Derry poet had encountered “at the edge of centuries”.

“We are indeed at the edge of centuries on these islands, with centuries of contention behind us, significant centenaries upon us and, I think, a very positive vista ahead.

“This edge of centuries is a good place to be, a comfortable plateau rather than a threatening precipice. There are, of course, further uplands ahead of us.

“But we can be optimistic about our prospects. At the edge of centuries lies a friendly, cooperative, respectful partnership,” he said.