British officials raised the prospect of erecting a physical border along the entire frontier between Northern Ireland and the Republic 30 year ago, declassified files show.

At a meeting between officials of both governments, the British said the idea of erecting a physical border along the lines of that separating East and West Germany was being considered.

The Irish officials responded strongly against the suggestion urging the British to drop it immediately.

The proposal, which would have seen posts erected across a 500 km distance, is contained in records made public by the National Archives today under the 30 year rule governing the release of State papers.

The main topic for discussion was cross-border incursions by the British army and the continuing IRA activity along the Border.

“Drawing on examples from recent years, we reminded the other side of the degree of seriousness with which incursions were regarded in the South and their capacity for generating political controversy,” the memo read.

The British responded by saying that incursions were always regrettable. They argued, however, that “their best efforts might not be sufficient to reduce significantly the occurrence of incursions, given the nature of the terrorist threat, the intensive security operation required to meet it, and the lack of clear physical delineation along the lengthy border”.

The British went on to say they were toying with two ideas which might impact on the number of incursions. The first was for more extensive communications between the British army and the Garda.

“The second idea under consideration on the British side was the possibility of physically delineating the Border along its full length. They cited, as an example, the frontier between East and West Germany which is delineated by posts set in the ground at regular intervals of five metres or so.

“We responded in very strong terms to this idea, arguing that it was unthinkable that it should ever be put forward seriously, and that if it emerged publicly, in any form, the impact on Anglo Irish relations would be disastrous. The British took these points on board.”