'(1) Where the parties are, or have been, linked by a contract of employment, the obligations of the employee are to be determined by the contract between him and his employer: cf Vokes Ltd v Heather (1945) 62 RPC 135 at 141.
(2) In the absence of any express term, the obligations of the employee in respect of the use and disclosure of information are the subject of implied terms.
(3) While the employee remains in the employment of the employer the obligations are included in the implied term which imposes a duty of good faith or fidelity on the employee. For the purpose of the present appeal it is not necessary to consider the precise limits of this implied term, but it may be noted: (a) that the extent of the duty of good faith will vary according to the nature of the contract (see Vokes Ltd v Heather); (b) that the duty of good faith will be broken if an employee makes or copies a list of the customers of the employer for use after his employment ends or deliberately memorises such a list, even though, except in special circumstances, there is no general restriction on an ex-employee canvassing or doing business with customers of his former employer (see Robb v Green [1895] 2 QB 315, [1895-9], All ER Rep 1053 and Wessex Dairies Ltd v Smith [1935] 2 KB 80, [1935] All ER Rep 75).
(4) The implied term which imposes an obligation on the employee as to his conduct after the determination of the employment is more restricted in its scope than that which imposes a general duty of good faith. It is clear that the obligation not to use or disclose information may cover secret processes of manufacture such as chemical formulae (see Amber Size and Chemical Co Ltd v Menzel [1913] 2 Ch 239), or designs or special methods of construction (see Reid Sigrist Ltd v Moss Mechanism Ltd (1932) 49 RPC 461), and other information which is of a sufficient high degree of confidentiality as to amount to a trade secret.
The obligation does not extend, however, to cover all information which is given to or acquired by the employee while in his employment, and in particular may not cover information which is only 'confidential' in the sense that an unauthorised disclosure of such information to a third party while the employment subsisted would be a clear breach of the duty of good faith.
This distinction is clearly set out in the judgment of Cross J in Printers and Finishers Ltd v Holloway [1964] 3 ALL ER 731, [1965] 1 WLR 1, where he had to consider whether an ex-employee should be restrained by injunction from making use of his recollection of the contents of certain written printing instructions which had been made available to him when he was working in his former employers' flock printing factory. In his judgment, delivered on 29 April 1964 (not reported on this point in the Weekly Law Reports), Cross J said ([1964] 3 All ER 731 at 738n):
'In this connexion one must bear in mind that not all information which is given to a servant in confidence and which it would be a breach of his duty for him to disclose to another person during his employment is a trade secret which he can be prevented from using for his own advantage after the employment is over, even though he has entered into no express covenant with regard to the matter in hand. For example, the printing instructions were handed to [the first defendant] to be used by him during his employment exclusively for the plaintiffs' benefit. It would have been a breach of duty on his part to divulge any of the contents to a stranger while he was employed, but many of these instructions are not really 'trade secrets' at all. [The first defendant] was not, indeed, entitled to take a copy of the instructions away with him; but insofar as the instructions cannot be called 'trade secrets' and he carried them in his head, he is entitled to use them for his own benefit or the benefit of any future employer.'
The same distinction is to be found in E Worsley & Co Ltd v Cooper [1939] 1 All ER 290, where it was held that the defendant was entitled, after he had ceased to be employed, to make use of his knowledge of the source of the paper supplied to his previous employer. In our view it is quite plain that his knowledge was nevertheless 'confidential' in the sense that it would have been a breach of the duty of good faith for the employee, while the employment subsisted, to have used it for his own purposes or to have disclosed it to a competitor of his employer.