Which legal principle or aspect best encapsulates the rationale for holding a banker strictly liable for honoring a forged check drawn on a customer's account, even if the forgery is executed with exceptional skill, barring any contributory negligence by the customer?

Consider the following statements regarding legal provisions in banking operations: Statement I: The Right of Set-off can be exercised across different branches of the same bank because the bank constitutes a single legal entity. Statement II: A Garnishee Order Nisi served on the Head Office of a bank acts as valid notice to all branches, provided reasonable time is allowed for transmission. Statement III: A banker's duty of secrecy is absolute and cannot be broken under any statutory compulsion. Statement IV: A bank automatically possesses a general lien over articles/valuables left in safe deposit lockers. Statement V: Under the Reserve Bank - Integrated Ombudsman Scheme, the Ombudsman can award compensation up to ₹20 lakh for loss arising directly from the act/omission. Which of the statements given above are correct?

A bank accidentally credits 2,50,000 to the account of Mr. Sharma instead of Mr. Verma due to a clerical error in the account number. Mr. Sharma withdraws the entire amount and spends it. Upon realizing the mistake, the bank requests the return of funds, but Mr. Sharma refuses. What is the legal relationship between the bank and Mr. Sharma regarding the 2,50,000?