A prototype ZX81 was demonstrated to BBC representatives in January 1981, while Sinclair's local rival Acorn Computers put forward their proposed Proton computer, a design – of which a prototype did not yet exist – based on the Acorn Atom.
Un prototipo do ZX81 foi demostrado a representantes de BBC en xaneiro de 1981, mentres a rival Acorn Computers propuxo o seu ordenador Proton, un proxecto —do cal non aínda existía aínda un prototipo— baseado no Acorn Atom.