I strongly suspect this is indeed a Staffordshire knot, but simply the top half is obscured by the shade created by the top of the cap.
The uniform is a very good match for that worn by the Staffordshire Yeomanry (Queen's Own Royal Regiment) from around 1905 onwards.
The basis of this uniform was the standard khaki introduced for the regular army in 1902, but the Staffordshire Yeomanry 'smartened' the standard uniform by adding an upright scarlet collar to the tunic, worn with a dark blue and scarlet coloured peaked cap, exactly as seen here.
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