slow march

(idiomatic, by extension) A progression or unfolding of events which occurs in an unhurried, steady, deliberate manner.

Example: 1849, Charlotte Brontë, Shirley, ch. 13:
  [T]he Rector emerged erect as a cane, from his garden, and proceeded in slow march, his hands behind him, down the cemetery.
c. 1851, Joseph Sheridan Le Fanu, "The Spectre Lovers" in Ghost Stories of Chapelizod:
  This was no other than a column of foot soldiers, marching with perfect regularity. . . . On they came at a slow march.
1946 Jan. 21, "Music: Berlin Hit," Time:
  Germany's newest song hit was hummed in streetcars, in movie theaters and at political meetings. . . . Its slow march tune was catchy, and its lyrics fitted Berlin's melancholy mood.
1835, James Fenimore Cooper, The Monikins, ch. 12:
  [S]ome spirits, more audacious than the rest, became restive under the slow march of events.
1904, H. G. Wells, The Food of the Gods, ch. 1:
  "[T]he venerable order, the broad slow march from precedent to precedent that has made our English people great and this sunny island free—it is all an idle tale."
2005 Oct. 17, Tom Dusevic, "Trust Me, I'm Fair," Time:
  For three decades, John Howard has been on a slow march to end centralized wage-fixing.