According to @HereGoesGabbi
Find a pub. Any pub. Order a local cider. I've yet to meet a pub here I did not love.
This was at The King's Head near Piccadilly
If you're hungry, order a meat pie. Hardy and delicious.
This was at The Champion near Kensington Palace
Pick up coffee and a pastry. Then, look up the closest park. Find a spot and soak in the beauty. I recommend Kensington Gardens/Hyde Park.
Be a tourist. Get a ticket for a hop on, hop off bus tour and see all the major sites like Big Ben, Tower Bridge and..
And, of course, give the Queen a wave at Buckingham Palace. You'll know if she's here based on what flag is flying.
Grab dinner at 10 Cases near the Tottenham Court Road stop on the Tube. Be sure to make a reservation and request to sit outside if the weather is nice.
Stroll through charming Seven Dials area full of shops and food.
You'll leave London, England inspired and ready to return for more. You can't see it all in 24 hours, but this was the perfect start.