PS -- I didn't use an Oyster Card for the Tube. I used Apple Pay on my Apple Watch, but you can use other methods of contactless pay. It worked great! In fact, I used it for 99% of my spending in the UK, even in Chipping Campden in the Cotswolds.
Thanks for these suggestions, Cameron! We're planning our 4th visit to London from Aug 26- Sept 5 prior to joining our tour of Slovenia and Croatia. We have rented an apartment across from the Vic and Al through Ivy Lettings. We have BBC Prom tickets, The Lion King, Bluegrass concert at Cecil Sharp House, and a day trip to Oxford and Ashmolean tickets to their Pompeii Exhibit. I just read your suggestion to Events Calendar that there is a Thames Festival starting Sept 1 -30! A river trip sponsored by the Brunel Museum looks fascinating!
For your Proms concert: dress for hot weather (there is AC but there are up to 6000 people there and stage lighting) - open necks and short sleeves are pretty well essential for all but the most cold-blooded. And please take in a bottle of water to help suppress any urge to cough.