You can have a mixed opinion about London but one thing you cannot deny - there is plenty of choice. And that is fantastic when it comes to eating out as a vegan. You might be lucky to have a completely veggie/vegan cafe or restaurant in you city but for a lot of vegans eating out can still be a struggle. If your friend group is not entirely veggie, you can feel isolated with your salad and chips (thank heavens for these safe options available at almost every dinning) while others are tucking into their far more exciting looking dishes. Do not get me even started on the dessert! After a few trips like this you would definitely start to dream of a local veggie cafe where staff can confidently advice according to your dietary requirements and do not confuse gluten free with vegan (these are not synonyms!).
For me, travelling to a new city always involves exploring what local vegan cuisine has to offer. In fact, most of the time going for a vegan snack is first on my to-do list (priorities, right?). My saviour is The Happy Cow mobile phone app (free version available) which allows you to search your area for vegan, veggie, veggie-friendly and health stores. The app also has the opening times, the price category, address, external links and sometimes reviews and photos from previous visitors. While the information is abundant, I would definitely advice you to check the official source (Facebook or website) of any particular place you are going to because I have been caught out with places being closed for vacation and moving to an alternative place.