If you are coming to London and have particular dietary needs, then here are a few words of advice.
Vegetarian/vegan
Our personal experiences of vegan or veggie food are very limited, but we do know that every restaurant or bar that we visit, and even the fast food places, have suitable options. These are usually marked very clearly.
The only places you may find choice more restricted is at the traditional caff (ie cafe) but even there choices are available.
Allergies
If you have an allergy, tell the people at the restaurant. Any good server will ask, sometimes more than once.
Even better, if you book on-line there will be a space in the form to record just that fact.
If you don’t tell them, they can’t know. They want you to enjoy your visit and not have complaints later. They should do everything they can within reason to cater for you.
Ask
If you are not sure about something, ask. If the waiter does not know and goes off to find out, or if they know but it’s not what you wanted to hear, then don’t blame them.
If they are telling you the truth, going out of their way to provide you with correct information, it’s not their fault. If you are not happy, go elsewhere.
Substitutions
In some countries you will hear an order like this:
“Can I have a fillet steak medium rare with bearnaise sauce and fries, except can I have chicken rather than steak, and mashed potatoes with an egg, and ranch dressing?”
The menu isn’t a starting point for negotiation, it’s what the place serves. If you want something different, why did you go there in the first place?
It’s perfectly fine to say “Can I have X but without y” (eg as I do, English breakfast without black pudding). If they can they will do it. Maybe they will suggest something else eg extra bacon.
