Your recommended activity is taking afternoon tea in the Fortnum & masons department store in London.
Here's an extract on F&M from our recent post on afternoon tea locations in London >>>
If you are looking for a location that offers a large selection for your afternoon tea, then you must stop at Fortnum and Mason.
They offer more varieties of tea than you can imagine. Thankfully, they also host a tea-tasting service to make your choice a bit easier. During the tasting, staff members will guide you through different combinations and blends so you can choose your favorite.
Your afternoon will be capped off by the presence of a live pianist and a selection of scones and pastries.
(Extract from The Top Places to Enjoy Afternoon Tea in London.)