Order & Pay lets a table order food and drink without leaving it. The research and testing here was about one question: at what point in the ordering journey do you ask someone about allergies, and what do you tell them back.

Ask too early and people skip it, because they haven't chosen anything yet. Ask too late and they've already paid. A table also orders together but eats separately, so one answer covering everyone is wrong for most of the people at it. And a pub kitchen with one fryer often can't promise a dish is safe at all.

Six testing sessions ran in person, in a venue, focused on where the allergen step belongs in the journey rather than how the screen looked. That moved the model to a per-diner declaration instead of one answer for the whole table, with a plain-language restatement of what was declared, shown on screen before payment. Edge cases for shared preparation, substitutions and amended orders were each written up and agreed with legal and kitchen operations.

The obvious build is a filter that hides dishes which aren't safe. It looks confident, and it hides the difference between "this is unsafe" and "we don't know". So every dish stays on the menu with its status written on it, including "may contain, shared preparation", which is the only honest answer a kitchen with one fryer can give.

The model shipped and is still the pattern in use. 4.5 million downloads and 40+ orders per second at peak Christmas trading are platform figures rather than mine, and no completion rate for the allergen step was ever shared with me.