Where would the Centurion stand in a battle line?

[Robert Vermaat]

I believe this was discussed before, in particular with the debate on who the antesignani were. By the etymology, they would have been troops specifically selected to stand in advance of the signum, indicating that the regular troops stood behind or level with it. The (very late!) command of the Strategicon of Maurice "nemo antecedat signum" ("let nobody march in front of the signum") could confirm this, if we can accept the huge gap in time between these sources.

Why 'very late'? Very much of Maurice's work goes back on a very long tradition. Besides, I consider 'very late' to be 13-14th century...
Seriously though, there's more. Roman cavalry traditionally had the commander at thye front, and from diagrams provided by Maurice we see this had not changed by the late 6th century. The same went for infantry commanders btw, when we look at the diagram for mixed formations.