Fast forward an hour, and I was on my hands and knees wiping gloop and gunge off the floor, and washing down the boy in the washing up bowl!
I'm not sure what I did wrong, but the recipe just did not work for me! In a frantic attempt to thicken the paint, I added a whole tub of custard powder AND a packet of icing sugar! So no paint, but a very sweet and starchy custard... :)
Oh well, I think the boy still enjoyed stirring it, and then sloshing it about all over the kitchen floor (this is where my huge Cath Kidston oiled tablecloth really came into its own!). Here are a few pictures, you can judge for yourselves whether or not it was worth the considerable effort!