The arrest of a man in Fermanagh in 1982 led to a breakdown in co-operation between the RUC and gardai, previously secret Irish state documents reveal.

The Dowra Affair, as it became known, involved Garda Thomas Nangle, a brother-in-law of the then Irish Justice Minister Seán Doherty.

Nangle was due to appear at the District Court in Dowra, County Cavan, on September 27, 1982, accused of assaulting James McGovern, from Fermanagh.

However, just hours before the case was due to be heard Mr. McGovern was arrested by RUC Special Branch officers on the basis of false Garda intelligence that he was involved in terrorism. His failure to appear in court led to the charge against Nangle being dismissed.

An article in The Sunday Times reveals that Sir John Hermon, the RUC Chief Constable, discussed the incident with Noel Dorr, the Irish ambassador to Britain. Based on previously secret Irish state documents, it quotes the Chief Constable telling the ambassador there were many things he knew about the Garda investigation into the Dowra affair which would be “astonishing if they came out”.

Hermon rejected the ambassador’s observation that the Irish authorities felt the RUC had failed to clear up its role in the Dowra affair. He said he had done everything possible, and claimed there had been many irregularities in terms of how the controversy was handled by the authorities “on the southern side”, which he could have pursued but did not.

The Chief Constable told the Irish ambassador that cross-Border co-operation had become poor, although he would never say so publicly for fear of giving ammunition to politicians “who would make capital of it”. He had expected co-operation to improve after Fine Gael came into power in November 1982, but in fact the situation had “seldom been worse”. He believed Fine Gael was either passively or explicitly telling Garda management to reduce co-operation with the RUC.

In a separate document, a civil servant noted a Northern Ireland official saying Irish authorities had not provided enough evidence of RUC wrongdoing in relation to Dowra which would justify setting up an independent investigation. There had not even been evidence of the RUC receiving a request from Dublin to carry out the arrest.

There was some reference to a phone call from Trevor Forbes, head of the RUC’s Special Branch, to the deputy Garda commissioner Joe Ainsworth to say “the job is done”.

The official noted: “But that was not evidence of anything - such expressions were common enough.” Ainsworth, who retired in 1983, following a separate scandal concerning the tapping of two journalists’ telephones, denies any knowledge of what happened in Dowra.

State archives show both governments were increasingly worried about the lack of co-operation between the police forces after the Dowra affair. Sir Alan Goodison, the British ambassador to Ireland, believed there was an unwillingness by senior gardai to communicate with their counterparts in the RUC.

Michael Lillis, a senior civil servant at the Department of Foreign Affairs in Dublin, said suspicion between the two forces had arisen due to RUC undercover officers conducting surveillance in the Republic of Ireland.

Lillis also said it was distressing that the previously excellent relationship between Peter Barry, the Irish Minister for Foreign Affairs, and Jim Prior, then Secretary of State for Northern Ireland, had suffered because of the issue. He also expressed serious concern that the Northern Ireland Office and the RUC believed the Irish government was conducting a vendetta against the police force, and against Hermon in particular.

Last year government documents released in Britain revealed that UK officials believed Garret FitzGerald, as Taoiseach, had political reasons for trying to find evidence of gardai doing improper favours for the Fianna Fail government led by his predecessor, Charles Haughey.

A memo written by FitzGerald in December 1983, after he met Sir Philip Woodfield, an official with the UK Foreign Office, also highlighted the rift between the two governments over the Dowra Affair. FitzGerald said the Irish government did not wish to do anything that would jeopardise Hermon’s position as he was an extremely effective police chief. However, the taoiseach said there was evidence of a conspiracy to pervert the course of justice in the Dowra Affair.

“The position is that our [garda] commissioner has lost confidence in the chief constable,” FitzGerald told Woodfield.

The Taoiseach also claimed Hermon had told Garda Commissioner Lawrence Wren that he would ask the Police Authority to appoint an independent chief constable to carry out an inquiry into the Dowra Affair.

FitzGerald said the Garda Commissioner had taken this to be an acceptance on the RUC chief’s part that something untoward had happened in relation to Dowra. The Taoiseach said Hermon appearing to go back on what he had said privately to Wren and that had led to distrust.

FitzGerald said that according to gardai, Forbes had considered resigning, but changed his mind and threatened that if he went, he would bring others with him.