This is a seminal contract law case regarding the formation of contracts in self-service shops. It established that goods displayed on shelves are not "offers" but "invitations to treat." The contract is concluded at the cash desk, not when the customer picks up the item. 

• The System: Boots operated a self-service shop where customers selected items, including drugs, from open shelves and placed them in a wire basket. They then proceeded to a cash desk at the exit to pay.

• The Supervision: A registered pharmacist was stationed near the poisons section, supervised the transaction at the cash desk, and was authorized to prevent the removal of any drug if necessary.

• The Charge: The Pharmaceutical Society sued Boots for infringing section 18(1)(a)(iii) of the Pharmacy and Poisons Act 1933, which required the sale of certain poisons to be effected "by or under the supervision of a registered pharmacist".

• The Argument: The Society argued that the "sale" occurred when the customer took the item from the shelf (completing the contract), meaning the pharmacist at the cash desk could not supervise the sale as it had already happened.

• At what point is the contract of sale concluded in a self-service shop: when the customer selects the item from the shelf, or when the cashier accepts payment?.

• Did the self-service system violate the requirement for pharmacist supervision under the 1933 Act?.

The Court of Appeal dismissed the appeal, affirming that the sale takes place at the cash desk under the supervision of the pharmacist, and therefore no offence was committed. 

• Invitation to Treat: The display of goods on shelves with price tags is merely an "invitation to treat" (an invitation for the customer to make an offer), not an offer to sell.

• Offer and Acceptance: The customer makes the "offer" to buy when they present the goods at the cash desk. The shopkeeper (or cashier) "accepts" this offer by taking payment.

• Practical Consequence: If picking up an item were an acceptance of an offer, a customer would technically be bound to buy any item they placed in their basket and could not change their mind or substitute it, which is not the intention of such a system.

• Supervision Compliance: Since the sale is only completed at the cash desk, the supervision by the pharmacist at that point satisfies the legal requirement of the Act.