Margaret Thatcher warned Northern Ireland's police chief that she would no longer send "her boys over in waves to be killed" in a rancorous row over who was to blame for the slaughter of eight soldiers in an IRA bomb.
Then RUC Chief Constable Sir John Hermon was upset by the "neo-colonial connotations" and "World War I overtones" of the Prime Minister's dressing-down, which he took as a distancing of herself from Northern Ireland, newly declassified files disclose.
The IRA detonated a massive roadside bomb containing 200lbs of Semtex explosive as a coach carrying members from the Light Infantry made its way along the A5 at Ballygawley, Co Tyrone, after midnight on August 20, 1988.
Eight soldiers - all aged between 18 and 21 - were killed and another 28 were injured. They had been making their way from the airport to their base at Omagh.
Six months later Sir John confided to a diplomat about the "panic reaction" from Downing Street in the wake of the attack, as well as tensions between the police and the Army over whose fault it was for the deadly security lapse.
The police chief, who was preparing to retire after almost 10 years in the role, and his wife Sylvia, now Lady Hermon, were dining with officials at the Anglo Irish Secretariat at Maryfield in Belfast on the evening of February 22, 1989.
The following day Irish diplomat Noel Ryan sent a missive to Dublin - marked 'Seen by Taoiseach' - about his conversation with Sir John, who he said opened up about his struggles with Thatcher as well as General John Waters, then commander of troops in Northern Ireland.
The primacy of the police over the military on security was under "constant threat" while relations with the Army "at times can be difficult", the police chief told Ryan.
Sir John "made clear" his "serious reservations" about the Army's 3rd Brigade, which included the UDR. "He fights his corner with General Waters, the GOC [General Officer Commanding], on this and other issues well, and recounted how when Waters had tried to put the blame for the Ballygawley bus bomb, which killed eight soldiers, on inadequate police intelligence, he made it clear to the PM that the incident happened because of inept Army security," Ryan reported.
"[Sir John] spoke in terms of the 'panic reaction' there was in the wake of Ballygawley and how he resented one particular utterance of the PM that she was not going to 'send her boys over in waves to be killed'.
"The neo-colonial connotations of that remark and its World War I overtones upset him and he saw it also as amounting to a distancing of herself and her Government from Northern Ireland."
In a wide-ranging conversation, Sir John was also "critical" of the Northern Ireland Office for its approach to relations between the security forces and the community.
The NIO "mistakenly in his view, see the issue of community relations as a matter for the Police Authority. In his view, this is the preserve of the Chief Constable".
"He believes the force is heading into a very difficult period over the coming two years with the twentieth anniversary of the 'troubles' this year and the tri-centenary of the Battle of the Boyne next year," Ryan reported.
"Public order issues will be very much to the fore and will require careful and delicate handling.
"For this reason, he regrets the force will not be in the hands of an Ulsterman."
In June 1989 Dublin-born Hugh Annesley took over as Chief Constable, the second last to take on the role before the RUC was replaced with the PSNI.
Sir John said he was to "some extent to blame" for his "failure to provide for a local successor" because he had "lost" three years on "other issues".
The diplomat took this to be a reference to inquiries into an alleged shoot-to-kill policy by the RUC during the 1980s, according to the files just released.