The 55-year-old Countess donned a smart-casual look for the occasion as she visited staff to see what their job was like first-hand.
Sophie was wearing a long camouflage print shirt dress, with double breast pockets and an elasticated drawstring waist.
The long sleeve French Connection dress is currently in the sale at just £60, half its original price.
It is already selling out fast and is now only available in smaller sizes as royal fans hope to copy the look.
However, other retailers have similar versions, including New Look which has a £24.99 dress with the same style and a slightly different camo print.