OK so the Spotless book doesn't have solution for leather but for removing ink from fabric it says this :

"Rot milk by leaving it in the sun. The time this takes depends on the weather and the age of the milk. Place the solids on the stains and leave until the stain starts to rise in to the milk solids, than wash the solids out using detergent and water."

sounds a bit wierd but can't hurt to try I guess ...........remembering this was for fabric.

Sounds like the stool comment wasn't far off the mark after all.