The three walks that I would consider to be the best would be the Lambeth and the South Bank Walk, the Fleet Street and St. Paul's Walk, and the Regent's Park Walk.
The Lambeth and the South Bank Walk took you through some of the city south of the Thames, then through Archbishop's Park and over to the Thames itself. The majority of the walk consisted of walking along the riverside, past the London Eye, past multiple bridges, until you finally cross the Waterloo Bridge past the Somerset House and get to the Temple tube station. This was one of the best walks because it allowed you to experience what you can only experience in London. The beginning allowed you to see typical parts of the city; the park was an enjoyable play area to walk through. Then the walk along the Thames was the perfect way to see the quintessential sights of London. From across the river, while casually strolling through the less-crowded boardwalk, you were able to see a clear and perfect view of Big Ben and the Houses of Parliament; soon after you were able to walk right under the London Eye. Beautiful views of the London skyline and sites such as the Somerset House could also be seen.
The Fleet Street and St. Paul's walk took you through the area to the west and south of St. Paul's. It leads you through winding streets, through pubs, alleyways, past churches until it takes you straight up Fleet Street with a perfect view of St. Paul's in the background. And then continues to take you through back ways and lesser known streets in the city until you end up back where you started at St. Paul's tube station. This is one of the best walks because this was the one walk that I felt like I really got into the heart of the city - not just tourist areas, but areas of the city where people actually live/work/socialize. It took you off the main roads and took you down streets and alleyways that you normally would never think to go down. You got to see notable churches and historical pubs that were interesting, but you also just got to see the normal pubs that young professionals go to after work. It took you out of the tourist bubble and into the heart of London.
The Regent's Park Walk led you south from Chalk Farm tube station and down to Primrose Hill, a grassy hill that gives you a complete view of the London skyline. Past Primrose Hill, the walk continues down past the London Zoo and through Regent's Park. Along the way you pass the Boating Lake and go through Queen Mary's Gardens, eventually leaving the park and walking along the road until you come to Regent's Park tube station. This was one of the best walks because it showed you the best of London's parks and city gardens. Primrose Hill and Regent's Park are both breathtaking beautiful and are huge. You get the best experience of London's natural beauty that still exists amidst the numberless buildings and apartments. It allows you to see the formality of the gardens, a trademark of British landscapes, but also the soft, natural green hills that are so representative of England as well.