Letters patent are still used in the United Kingdom, for example to confer peerages and to appoint judges, but under the present Patents Act are no longer used to grant patents for inventions. Prior to 1878, letters patent for inventions were engrossed on parchment and bore the Great Seal in wax. Subsequently paper was used and a wafer seal of the Patent Office replaced the Great Seal, but the wording of the letters patent document (not to be confused with the printed patent specification) was still very impressive. British patents were still being granted in 1981 in the form of a command from the Queen to her subjects to refrain from infringing the patent under pain of the royal displeasure. Unfortunately for the patentee with a taste for this sort of thing, under the Patents Act 1977 all that he gets is a very unimpressive certificate of grant from the Patent Office.
It is important to realize that the rights given by a patent do not include the right to practice the invention, but only to exclude others from doing so. The patentee's freedom to use his own invention may be limited by legislation or regulations having nothing to do with patents, or by the existence of other patents. For example, owning a patent for a new drug clearly does not give the right to market the drug without permission from the responsible health authorities, nor does it give the right to infringe an earlier existing patent. In the very common situation where A has a patent for a basic invention and B later obtains a patent for an improvement to this invention, then B is not free to use his invention without the permission of A, and A cannot use the improved version without coming to terms with B. The right to prevent others from carrying out the invention claimed in a patent may be enforced in the courts; if the patent is valid and infringed the court can order the infringer to stop his activities, as well as providing other remedies such as damages.
It is also important to distinguish between ownership of an invention or a patent and ownership of goods which incorporate the invention or fall under the patent. The question of who owns the goods is completely different from that of who owns the patents. Unlike the situation with regard to copyright, infringing goods do not become the property of the patentee, and even if the patentee has manufactured the goods, once he has sold them he usually can retain no control over their subsequent use or resale. The fundamental distinction between the ownership of patents and the ownership of things which are patented is often misunderstood or deliberately misrepresented, so that for example patents granted for transgenic animals are described as giving ownership of 'life' and patents for isolated human genes are talked of as if they gave property rights over human beings.
A patent is nevertheless a piece of property, and may be a very valuable one. Although intangible property, it may be dealt with in the same sorts of ways as tangible property such as real estate. Just as the owner of a house may live in it himself, sell or rent it to another, mortgage it, or even have it demolished, so a patentee may keep his patent rights, assign the patent to someone else, grant someone else a license to do something covered by