The ban came as a reaction to Kapoor gaining the exclusive rights to the worlds blackest pigment - otherwise known as Vantablack- in 2016. Semple write on his website ''This ultra-bright paint by Stuart Semple is available to everyone except Anish Kapoor! (who won't share his black!).''
At the checkout on his site, Semple requires customers to agree to a declaration that ''(they) are not Anish Kapoor, (they) are in no way affiliated to Anish Kapoor, (they) are not purchasing this item on behalf of Anish Kapoor or an associate of Anish Kapoor. To the best of (their) knowledge, information and belief this paint will not make its way into that hands of Anish Kapoor.''
The pigment can be anyone's - well apart from Kapoor's, apparently - for a mere £3.99. It is currently sold out until later this month.
Despite his attempts to block Kapoor, the artist managed to get his hands on a pot of the pink powder. In retaliation, the artist posted an image of his middle finger coated in the pink pigment, with the caption: ''Up yours #pink.''