Let any mud dry and bruxh off any large pieces.
Spot clean the canvas using a damp sponge,
rubbing in the direction of the drilll of the fabric.
It is best not to use a cleaning cloth that is too abrasive such as a scouring pad as this will lift the pile of the fabric.
More stubborn marks can be removed using a small brush such as a toothbrush and a small amount of mild hand-washing detergent, again rubbing in the direction of the drill.
Blot with a clean absorbent cloth and leave to air-dry at room temperature.
Pad out the bag and its pockets with paper to maintain its shape whils drying.
Do not immerse the bag in water or wash in a machine.
The fabric and leather components of your bag are not suited to being soaked in water or detergent.