London Sunday Afternoon/Evening Plan Suggestions?

Well, the Globe is within walking distance. Much Ado About Nothing that night at 6:30 - if you can keep awake. I am a fan. I am also a fan of your hotel. Great central location. If it were me, I would research self-guided tours with a handy map (I am old-fashioned that way) and perhaps a read through a guide book. Here is an example from London Toolkit. I don't think you will make it into town for a 2 or 2:30 London Walks tour. And for me, the 7:30 pub crawls would be too late on day of arrival. You might check out London Walks for Monday, though.

I do not have specific recommendations for eating. Southbank is lovely and interesting to stroll along. There are restaurants along the way - though maybe another poster will have a great recommendation. You can walk down to Borough Market on Monday, but it is closed Sunday.

Enjoy your research and your trip.

Oh, PS, Westminster Bridge and the area around the Eye can be extremely crowded. Do not be put off. You can get away from the crowds pretty easily. As I recall, the front of the hotel is quiet as it faces away from the Eye.

A traditional Sunday feast, featuring roasts, has become popular (again) in some pubs. The midday rush should be waning by the time you settle at your hotel. Don't wait until supper since some of the roasts may have run out. An early-evening stroll to let things settle and then early-to-bed.

Agree about Sunday roast, but if you're in the mood for something lighter the map shows several casual eateries on your side of the Thames, an easy walk from your hotel.
Apart from a meal, if the weather is decent I'd recommend walking around rather than a sit-down activity. You'll be right by the London Eye and if you cross the Thames there's lots to see at Parliament Square & surrounding it. If you really want to stretch your legs, you can take Birdcage Walk all the way to Buckingham Palace.

Walk across Embankment Golden Jubilee Bridge.

There’s a Dishoom restaurant as well as either the Sherlock Pub or Princess of Wales Pub. Lots of other food options by the Princess of Wales on Watergate Walk.

Then walk along the Thames Path toward Parliament and Westminster Bridge and back to your hotel.

Use Google Maps satellite street view to see what I’m referring to.

Thanks for all the great suggestions! I'm guessing we would need to make reservations for Sunday Roast? And Dishoom is definitely on our list, as we've seen it recommended over and over!