The nineteenth-century engineering hero Isambard Kingdom Brunel was a prominent patent abolitionist in debates about the patent system in Britain. His opposition is usually regarded as principled, that is, based in liberal laissez-faire opposition to monopolies and to the constraints of bureaucracy. Against this it is argued that Brunel's views on patents evolved. As late as 1840, despite lessons about patents from the bad experiences of his father, Brunel could still consider taking out a patent himself, something that a decade later he denied he had ever contemplated. Brunel's engineering persona, his experiences and conduct of engineering practice were the base from which he eventually formulated principled opposition to the patent system. The paper examines his responses to importunate inventors who pestered him with inventions in the 1840s and elucidates how he dealt with the patented inventions of others that he wanted to use in his projects. It is suggested that for Brunel patent abolitionism was in effect a way of doing business before it became a political cause. The case suggests the value of approaching the history of patents and, by implication, of intellectual property more generally, through detailed examination of practices.