Very hard to remove.
[broken link removed] shows this:
"Read the care label fully first. Begin by rubbing the stain with white vinegar. If this doesn’t work, soak it in methylated spirit (take care when using it) for an hour. Place the rest of the garment above the area being soaked to avoid the solution being wholly absorbed by the garment. Always check the garment for colourfastness before using methylated spirits. If the stain persists, rub the stained area with laundry soap and water – as hot as the fabric will allow. Then soak overnight in Persil Biological and warm water. After this, wash normally."
[broken link removed] might be worth a try.