This article on London's most interesting bus routes has probably been posted before, but I am posting again for the benefit of many who are new to the forum and have yet to visit London.
https://londonist.com/2016/10/london-s-best-bus-routes-for-tourists
We enjoyed using the bus instead of the tube on our last trip (3 weeks in London). The 15 was particularly useful for us; we could take it as far as Tower Bridge and then walk across the bridge to our apartment on the south bank.
We also had a nice ride on the 11 down Kings Road to Worlds End and Chelsea Harbour pier. We sat upstairs in the front seats, and a friendly local provided some commentary on what we saw as we passed by.