What is the test for determining who is liable for food poisoning?

The closest counsel for the plaintiff was able to come was the English case of Lockett v. A. & M. Charles Ltd., [1938] 4 All E.R. 170. This was an action by a husband and wife for food poisoning suffered by the wife following lunch at a hotel. It was agreed that both ordered their food; however, the husband paid for the meal. It was held that the wife was entitled to succeed as she was entitled to recover damages for breach of the implied warranty that the food supplied was fit for human consumption. The question of who paid for the meal was discounted by the learned trial judge as an important fact as he said [p. 172]: I think that the inference is that the person who orders the food in a hotel or restaurant prima facie makes himself or herself liable to pay for it, and when two people — whether or not they happen to be husband and wife — go into a hotel and each orders and is supplied with food, then, as between those persons and the proprietor of the hotel, each of them is making himself liable for the food which he orders, whatever may be the arrangement between the two persons who are eating at the hotel. It can be seen in that case the court did not rely on agency but treated the husband and wife as both contracting parties with the restaurant.