What is the standard for reasonable care and skill of a bank?

Although Bull J.A. was in the minority as to part of his reasons, Robertson J.A. who gave the reasons for the majority quoted with approval the following passage of Ungoed-Thomas J. in Selangor United Rubber v. Cradock (No 3.) (supra): . . . To my mind, in accordance with those quotations, a bank has a duty under its contract with its customer to exercise 'reasonable care and skill' in carrying out its part with regard to operations within its contract with its customer. The standard of that reasonable care and skill is an objective standard applicable to bankers. Whether or not it has been attained in any particular case has to be decided in the light of all the relevant facts, which can vary almost infinitely. . . . In Groves-Raffin (supra) there was evidence of the practice of a reasonable banker when faced with an unusual transaction.