Margaret Thatcher’s chief legal adviser believed prosecutions would “go high as chief superintendent” within the RUC over an alleged shoot-to-kill policy in Northern Ireland, newly released files reveal.

Sir Michael Havers, then attorney general, told SDLP leader John Hume during a lunch in April 1987 there would be “shocks felt throughout the force” over the Stalker inquiry.

During the meal, arranged by Richard Ryan of the Irish embassy in London, who reported back to Dublin about it, Havers was “quite forthcoming” on what was one of the most controversial episodes of the Troubles.

“He said he now has grounds for believing that he will be undertaking prosecutions within the RUC ‘which will go high, as high as chief superintendent’.

“He said he does not think that [then chief constable Sir John] Hermon himself will be brought down by it, but that there will be shocks felt throughout the force.”

Former police chief John Stalker was asked to investigate RUC shootings of six people but was removed from the inquiry shortly before it was due to report in 1986. The inquiry was taken over by another English police chief but its findings were never made public.

At the meeting, Havers told Hume he intended to “bring forthrightness” to the case.

“Havers said that if they think they can operate that way, then he has every intention of rooting them out,” Ryan reported.

Hume told Havers a public indication of imminent prosecutions could be “extremely valuable” to his party’s prospects in the Westminster elections later that year.

The SDLP leader said it would be “just the thing to knock off Gerry Adams and, just possibly, Enoch Powell” in the West Belfast and South Down constituencies.

“Havers responded strongly to this and mused a bit out loud about how much he might possibly be able to engineer it,” according to the file marked confidential.

“He was, he said, very taken by the idea of bumping off both Adams and Powell in one go.”