London is an incredibly walkable city and although I still maintain the best way to see it is from the River, walking is the second best way to do so. There are a number of tours to introduce you to London but one I have taken time and again is with Walks of London who has a plethora of tours exploring London, old and new. Some of my favourite include Harry Potter Film location walks, Kensington Royal Village and Knightsbridge Pub walk. There’s plenty to choose from, simply turn up and it cost you less than a tenner. the guides are incredibly knowledgeable and fun.
Side Note:
If you book one tour, book a tour with Look Up London: Katie runs incredibly informative tours in and around London, a certifies blue badge guide, her tours are unique and interesting. The feminist Jack The Ripper tour is top notch.