alternative touristy London

The views from Primrose Hill?

I'll be honest and say that my RS books are not new, I don't have a clue what's in the current book. So I wouldn't want to duplicate. If it is in there please excuse.

Brompton Oratory...

Mudchute Farm...

The rooftop garden on top of the HS2 building in Canary Wharf... Or the view from the top of One New Change... Or the Sky Garden in the Walkie Talkie Building.

Leadenhall Market...

Walking in the Royal Parks, Richmond, Bushey, Kensington

You might try:
1) Kew Gardens - awesome during the Spring, Summer and fall
2) Hampton Court Palace
3) Covent Garden ( lots of shops and booths)

Hope this helps!

Walking tours, either with a walking company or cobbled together on your own.

London Walks - From their website they do not appear to be up to full strength with their walks which does not surprise me. I've done a number that are thru neighborhoods - Highgate Village, Chelsea, Belgravia and several that are theme-based such as WWII. It's gotten me in to some nooks and crannies I would have missed on my own.

https://www.walks.com/

https://sixinthecity.co.uk/walks/ - I've not walked with this company but they have some interesting themes. I'm interested in their church walks

https://www.aladyinlondon.com/2018/08/london-walking-tours.html - I've done several of her self-directed walks or at least pieces of them. Some in the way she has them set out, some going backwards from a hotel I was staying in, lol.

I've bookmarked this link to London's Royal Parks which includes Brompton Cemetery which is on my list for next time.

https://www.royalparks.org.uk/

Have you done a verger tour of Westminster Abbey?

Wallace Collection?

Apsley House (Duke of Wellington)?

Temple of Mithras? https://www.londonmithraeum.com/

If you want off the wall places many tourists never see, consider:

Walk the Roman wall
guildhall
The former Whitechapel bell foundry where the Liberty Bell was cast
The original Twining’s tea store
Neal’s yard dairy and/or Paxton & Whitfield cheese stores
Paddington bear statue at Paddington station
Church service at the Queen’s chapel or St. James Palace
Cleopatra’s needle
Little Ben by Victoria station
Little Venice
Camden Lock area
Bank of England museum
Fortnum & Mason store
Liberty London and Carnaby street
The Golden Hinde replica ship
Filming locations seen in the Notting Hill movie or As Time Goes By tv series
Benjamin Franklin’s house
Sewer Lamp - the last 1870s destructor lamp used to burn off methane from the sewers
Republic of Texas plaque, home to the Texas Legation 1842-45
Pickering place where the last duel in London took place
Hampstead Heath
Highgate cemetery
Victoria Park market
Burdett-Coutts Drinking Fountain, 1862 fountain that provided fresh drinking water to the poor.
Columbia Road Flower Market
John Snow water pump, Source of cholera outbreak. 1854 Snow discovered cholera was spread via water

Just get on any double decker bus, sit upstairs, and travel the length each one's journey.
Lots to see from up high.
Just make sure you have a bus app or map so you can get back from the end of the line!

Pam’s suggestion of tours with London Walks is excellent. Add their Marylebone walk to the tours to consider.

Then there’s The Banqueting House. It’s right downtown, along Whitehall Street. It was part of Whitehall Palace, the rest of which burned down over 300 years ago. It was used for royal banquets 400 years ago, as well as performances for the kings and queens. The ceiling is covered with elaborate paintings by Reubens, almost a Sistine Chapel for London. They have period costumes for you to dress up in for photos in front of a throne as well, if you like.

It’s almost hiding in plain sight of other major historical and engaging attractions. King Charles the First emerged from the building and was beheaded just outside, during the English Civil War in the 1600’s. You’ll have a better time than he did.

These are not in the RS guide to London:

The Design Museum. The permanent collection is free/donation requested. There is often a special exhibition with an entry fee. I'd also recommend the Leighton House nearby, but it is currently closed (I'd guess due to COVID-19).

Eltham Palace if interested in Art Deco. Also has a medieval great hall.

If you like the art of William Blake, the outdoor display of mosaics based on his work is worthwhile. I stumbled on it while walking from my South Bank hotel near Waterloo Station to the Imperial War Museum, but the Atlas Obscura website has an entry for it: https://www.atlasobscura.com/places/william-blake-mosaics-lambeth. Free.

If you happen to have skipped the Imperial War Museum (in the book, of course) due to lack of interest in war materiel (as I almost did), take a look at the museum website. I've found the permanent collection very interesting, and there are always some small special exhibitions as well. The museum is free/donation requested, and I've never encountered a special exhibition with an entry fee. The audio guide is good, but it pretty much duplicates material posted throughout the museum, so just choose whether you prefer to read or listen.

Wikipedia has a useful list of London museums (loosely interpreted): https://en.wikipedia.org/wiki/ListofmuseumsinLondon. Lots of possibilities there, but do check to be sure places of interest are open.

Definitely in the book but always good for an introduction to a new neighborhood: London Walks.

Holland Park (with its Kyoto Garden and waterfall)
Regents Park (Zoo and cafes)
Postman's Park (north of St Paul's Cathedral)
Leadenhall Market (Victorian; already mentioned by Nigel, but compare it to the following building while you're there.)
Lloyd's of London building (An ultra modern office building; looks like a stack of tin cans. Built right next to Leadenhall Market. Stark contrast between the two.)
Spitalfields Market
Smithfield Market
Museum of London
Museum of London Docklands (Canary Wharf)
London Canal Museum (near King's Cross)
Regent's Canal boat ride from Camden Market to Little Venice
Temple Church (built by the Knights Templar as their English headquarters and some are buried there inside the church)
All Hallows-by-the-Tower (a section of Roman road and floor of a Roman townhouse can be seen in its basement)
Southwark Cathedral (Shakespeare's brother is buried there)
Courtald Gallery/Somerset House
Lambeth Palace, or at least its gardens
St. James's Palace (admire the Tudor exterior; no admittance for the public)
Greenwich (National Maritime Museum, Cutty Sark, and a weekly market)
The Thames Path (walk as far as you want--all the way to Windsor or to Oxford if you wish)
Battersea Park (with its cafe and pagoda)
London Wetlands Centre
Wimbledon
Richmond
Richmond Park
Syon Park
Syon House
Ham House
Strawberry Hill House
Another vote for London Walks

We enjoyed the Museum of London and the V&A Museum of Childhood.

Rebecca mentions the canal boat ride. We did it the opposite direction, from Little Venice to Regent’s Park, past part of the zoo (no animals seen from the canal). Once you’re off the boat, spending time in “hip” Camden Market area, or backtracking a bit to visit the zoo or stroll the park and see swans on the lake are possibilities.

Have a pull at the Ye Olde Mitre Pub!

Well, you've opened a can of worms because as you see we can give you enough to see to last the rest of your life!

Rebecca mentioned Lambeth Palace which made me think of the Garden Museum. I've got in on my "to-do" list, lol and it's been there for a few years! Probably only of interest if you all are interested in Gardening, though.

https://en.wikipedia.org/wiki/Garden_Museum

Also, I'm interested in Birding and the London Wetland Center is also on my list but it might not be what I'd want to see in December.

https://www.wwt.org.uk/wetland-centres/london/

Since you are going in December, Kew Gardens has a special Christmas lights program. There are timed entry tickets which might or might not still be available.

Here’s something I hope to do someday but RS does mention it in his book: https://www.camdenmarket.com/journal/camden-lock-take-a-canal-tour.

As I saw them for the first time yesterday I’m going to suggest the Crystal Park Dinosaurs.

Agree you should immediately check on line to see if any tickets still available for Christmas at Kew Gardens. Booked my tickets for Nov 28th months ago.

If a church Is within walking distance from where you are staying attend a Christmas Eve mass.

If this is your first Christmas in London you’ll need to know public transport ( busses, trains and the Underground) shut down Christmas Day. If not staying in an apartment with a kitchen consider reserving dinner somewhere. Many restaurants will closed but with London’s ethic diversity you’ll find a place for dinner.

Book a Panto. Check out Timeout London on line NOW for Santa Runs, choral performances, music, gallery offerings, and theatre offerings.

See the Christmas lights on Oxford, Regent and Bond streets. Walk along the Thames Path by the Millennium Wheel and enjoy the food booths.

Visit Leadenhall Market
Visit Spitalfields
Visit Maltby Market
Walk Along The Regents Canal
Take a tour of Highgate Cemetery
Walk along the Thames Path
Look for Elk in Richmond Park
If within walking distance of Hyde Park get up early Christmas morning to watch the Peter Pan Cup Race in the Lido

Enjoy your visit.

I second the London Museum. And honestly, it takes more than one or two trips to really absorb the British Museum.

Lets see...

If you are into music at all, or just want some music history, try taking one of the Beatles walks that start from Marylebone station. Fantastic walks that take you to and through places you probably would never go.

Having a pint at Ye Olde Mitre is fun (as was recommended above), but so is finding it if you've never been. For that matter, you can make a day of finding some off-the-beaten path pubs while you explore the city. TTry the Uxbridge Arms in Notting Hill, the Grenadier behind the Luxembourg embassy, or the Horse and Groom off of Belgrave Square. The Anglesea Arms off of Onslow Gardens or The Ship off of Gate Street or The Duke of York off of Dering Street or the Narrowboat off of Baldwin Terrace. In some cases, simply finding some of these places is half the fun, and with a good pair of walking shoes, you can explore the city.

Finally, you could take a 'Boris Bike' tour of London. 'Boris Bikes' as they are known locally are a bicycle hire scheme that started when Boris Johnson was Mayor of London. Essentially, hop from bike docking station to bike docking station no more than 30 minutes apart. If you do that, you only pay for one rental. You can make your way across the entire city this way. With a little reseach, you can take some off the beaten path routes.