I'm looking for somewhere fancy to go in Central London for afternoon tea. It will be in mid March this year so definitely not interested in anywhere that would need to be booked months in advance, thanks. 
Very flexible on cost as it's a big birthday and I want it to be a real treat. Would prefer a place without a strict dress code but will consider all recommendations. Must have good vegetarian options and nice cake!! Also, food should be plentiful as we will be going in early evening before the theatre and it will replace our evening meal. And surroundings need to be sumptuous please!