Working Horses (Shire Horses)

Very large Victory "Gold Box" puzzle with "period" scene as tractors have replaced working horses in most of England.  Photo. Horses are strangely hitched in photo.  Usually, they are hitched and pull together.  Anyone explain this to me?  The Shire is a British breed of draught horse. It is usually black, bay, or gray. It is a tall breed, and Shires have at various times held world records both for the largest horse and for the tallest horse. Wikipedia