The Norwich Pharmacal order is an exception to the general rule that only people who are actually named as parties to existing litigation are obliged to disclose documents and other materials relevant to the claims. It is in this respect that it differs from the Anton Pillar/Search and Seizure Order
For example: If X sues Y for fraud, X can usually only obtain relevant documentation from Y. However X cannot usually call for Z to provide documents, even though Z may have relevant or even key information. Z would normally only be obliged to produce this kind of information following a court order.
Norwich Pharmacal Co. v Customs and Excise Commissioners 
The Claimant was the owner and exclusive licensee of a patent for a chemical compound, furazolidone. Unlicensed consignments of the compound were imported into the UK, and constituted infringements of the patent. The Defendants had records of the identity of the importers. The Claimant had failed to determine the identity of the importers and brought a claim against the Defendants, for amongst other things, an order for disclosure of the names and addresses of the importers of furazolidone, the quantity imported by each importer and any other relevant documentation.
The Defendants objected to production of the documents on the basis that such disclosure would be injurious to the public interest because they contained confidential information.
The patent was assumed to be valid and the imported consignments, infringements. The Judge granted the order for disclosure. The Court of Appeal allowed the Defendants appeal and the Claimant appealed to the House of Lords.
Allowing the appeal and granting the order for discovery it was held that:
- Discovery to find the identity of a wrongdoer was available against anyone against whom the claimant had a cause of action in relation to the same wrong. However, it was true as a broad and general rule that a court would not order discovery against a mere witness or a party against whom no reasonable cause of action existed. An order for discovery was not available against a person who had no other connection with the wrong than that he was a spectator (e.g. against a bystander to a road accident who happened to note the licence plate number of the car) or had some other document relating to it in his possession.
- On the other hand, if through no fault of his own a person became mixed up in the tortious act of others so as to facilitate their wrongdoing, he might not incur personal liability, but he came under a duty to assist the person who had been wronged, by giving him full information and disclosing the identity of the wrongdoers. It did not matter whether he became so mixed up by voluntary action on his part or because it was his duty to do what he did.
- This principle would operate regardless of whether the person mixed up, incurred any minor liability, and whether or not proceedings were brought against him. In the circumstances the public interest lay in granting the order sought.
- Lord Reid and Lord Cross of Chelsea stated that a party concerned about the propriety of making such disclosures was entitled to require the matter to be submitted to the court at the expense of the person seeking the disclosure.
House of Lords in Ashworth Hospital Authority v MGN Ltd 
“The Norwich Pharmacal case clearly establishes that where a person, albeit innocently, and without incurring any personal liability, becomes involved in a wrongful act of another, that person thereby comes under a duty to assist the person injured by those acts by giving him any information which he is able to give by way of discovery that discloses the identity of the wrongdoer.”
Smith v ADVFN PLC  EWCA
The Court of Appeal considered the proper ambit of a Norwich Pharmacal order and, in particular, the coherency and quantity of the evidence supporting a Norwich Pharmacal order. The court held an applicant should be careful to provide the courts with a coherent body of data from which an allegation of wrong doing could properly be assessed.
The case gives valuable guidance not just on the nature, but also on the presentation of the evidence in support of a Norwich Pharmacal application. An indiscriminate and disorganised mass of material could be fatal to the application.
The case confirms that although Norwich Pharmacal relief is a useful tool in the litigation process, enabling a claimant to get documents and affidavits from a third party, it should be used with caution. If the claimant can get the documents from another source or by other means, the court will not grant the orders and the claimant may find itself facing the third party’s legal costs”. Source Freshfields