Capitalisation of establishment

I've read several pieces about capitalisation of the word 'government' in different scenarios, but how about with the word 'establishment,' as in "the British establishment of the day condemned the action". Do I capitalize as I'm referring to a particular one in a particular time-period and it therefore has the sense of being monolithic, or, as it is inherantly a loose term, does it avoid such rules?

The American philosopher and poet Ralph Waldo Emerson was the first to use the word establishment in a sociopolitical sense without further modifiers:

Conservatism never puts the foot forward; in the hour when it does that, it is not establishment, but reform. — Ralph Waldo Emerson, “The Conservative,” Lecture, Masonic Temple, Boston, 9 Dec. 1841.

There are always two parties, the party of the Past and the party of the Future: the Establishment and the Movement. — Ralph Waldo Emerson, “Historic Notes to Life and Letters in New England,” 4 Feb. 1880.

Emerson’s new meaning does not appear to have taken hold except for a few scattered attestations in the 1920s:

Once and for all Englishmen were to be shown that revolt against the Establishment was not to be tolerated. — John Drinkwater, Oliver Cromwell, New York, 1927. COHA

The term was discussed systematically — and entered common discourse — in the Sept. 1955 number of the British magazine the Spectator by journalist Henry Fairlie:

By the Establishment, I do not only mean the centres of official power—though they are certainly part of it—but rather the whole matrix of official and social relations within which power is exercised. The exercise of power in the United Kingdom (more specifically, in England) cannot be understood unless it is recognized that it is exercised socially. — The Spectator, Sept.1955.

As the two passages from Emerson already suggest, there is no consistent use of upper or lower case, though once the term became, as it were, established, capitalization becomes less common. A more frequent technique, particularly in newspapers, was to put the word in lower case but bracket it in quotation marks to mark a novel meaning:

The first group of British authors he discussed were the “angry young men,” who are similar to Beatniks. These authors, Bode disclosed, are protestants against the “establishment.” — Daily Kent Stater (Kent OH), 10 Mar. 1960.

“I’ve become the symbol of the attack against the establishment,” he had told his fellow veterans. “I’m not a brutal person, but remember the attack against the police has been used since time immemorial to attack the establishment.” — William W. Turner, The Police Establishment, 1968, 83.

The writers say studies must be made to identify those governmental procedures and institutions which turn increasing numbers of youngsters against the Establishment, and an action program designed to change those institutions and those practices. — Desert Sun (Palm Springs CA), 14 Apr. 1971.

Later sources are just as inconsistent:

The whole discussion was punctuated by unrestrained outbursts from a veteran who seemed to have a grudge against the Establishment (represented by the politicians and General William Westmoreland), and by actress Liv Ullman, who provided the chorus by periodically shouting “What about the children?” — Synapse (UCSF student newspaper), 17 May 1990.

The situation is a little like the role of the Establishment in art in England in the nineteenth and early twentieth centuries. What was hung in the annual exhibitions of the Royal Academy was determined by established convention and taste, not by new ways of viewing the world. — Eleanor J. Gibson, An Odyssey in Learning and Perception, 1994, 283.

The Karen Finleys and Robert Mapplethorpes of the art world, and their many champions, are not disenfranchised outsiders, railing against the establishment: on the contrary, they are the establishment. — Hilton Kramer, Roger Kimball, Against the Grain, 1995.

Arturo is a mysterious and enigmatic Banksy-like artist known in the art scene for his playful actions against the establishment. — Program, Input Conference 2013.

A man who fought hard against the Establishment to put an end to campaign financing misdeeds. A maverick, really, who seemed to have a real independent streak and whom even Democrats trusted to follow his conscience for the benefit of us all. — Joan Wile, Grandmothers Against the War, 2008.

With a modifier such as British or American, both forms are also found, as in these two works published in the same year:

The prime movers controlling the British Establishment constitute a very narrow group of less than five hundred individuals. — Peter Childs, Michael Storry, Encyclopedia of Contemporary British Culture, 1999, 170.

For three years the king and Mrs. Simpson had carried on their affair under the knowing eyes of her husband and a large part of the British establishment, but without the knowledge of the British public. — Edward Digby Baltzell, Howard G. Schneiderman, The Protestant Establishment Revisited, 1999, 79.

Althouth the word first appeared in a time when abstract nouns denoting universal concepts such as Truth, Beauty, or Salvation were often capitalized, broader usage of establishment in this sense occurred after the Second World War, when an upper case establishment seemed decidedly unmodern. Few authors today, for instance, write: separation of Church and State as it was consistently written in the 19th c., though some still do.

So basically, you can choose whichever form you prefer, though the clear trend does suggest using lower case.