London Pass

The London Pass is not usually a good value.

For some things it does cover, like the Churchill War Rooms, you have to stand in the regular ticket line to get in. It's much better to purchase a timed entry ticket online FROM the Churchill War Rooms website.
https://www.iwm.org.uk/visits/churchill-war-rooms

There are also a lot of museums in London that are free including the National Gallery, British Museum and Victoria and Albert Museum. I see it lists the Tower Bridge as a sight and that is easily seen from the outside which to me is the most interesting part.

You'd really have to run the numbers to see if it would be a good value for you by going to the official websites of the places you want to visit.

Do be sure to look at your big sights and see if they have an official app to download. The Westminster Abbey app is excellent and easier to use than the free audio guides they have. Just have to remember to have your earbuds in your pocket!

For many travelers it isn’t. I’d decide what you want to see in London and then decide if the pass makes sense. The drawbacks are that it ties you to a pretty rigorous sightseeing schedule and it covers a lot of sights that are not near central London or might be considered second rate. The major museums are free. It’s also nice for a trip of that length to take a day to relax, perhaps walk along the Thames or a park.

However, if bought at a discount such as one of their frequent sales, it might make sense. Get a couple of guidebooks and make out a list of what you want to see. Keep in mind that some of the sights such as the Tower of London and Westminster Abbey are amazing, but you may tire of the crowds.

The one thing I wouldn’t do is let the pass drive your itinerary. Decide what you want to do and do it rather than making sure you get full value from the pass.

If you're tempted by the "skip the line" feature, note that it only applies to a very few attractions, and doesn't let you skip the security line.

I have fought with this too for a few years.
If you think you can pull off 3 or 4 attractions a day, then you might benefit from it.
I personally can't justify it based on the fact that we wouldn't be able to do enough in one day to cover the cost of it.
We just do 1 or 2 so it doesn't help us at all.
The skip the line thing seems cool though!

Again, at this time the London Pass only allows you to skip the line at the following six attractions:

Tower Bridge Exhibition
St. Paul's Cathedral
Hampton Court Palace
London Zoo
London Bridge Experience
Kew Gardens

I don't know which of these have significant lines normally, but it's hard to imagine the London Bridge Experience or Tower Bridge Exhibition do.

Note that it does not allow skipping the line at the Churchill War Rooms, which now have long lines.

With 10 days, a pass may become worthwhile, as you only have to see or do 1-2 covered things per day. Since it includes boat and HOHO bus tours, and you'll have time to take a day for Kew Gardens (for example), it's a potentially better deal than for those trying to make a 3 day pass pay (which requires running around like a chicken without a head, and skipping lots of worthwhile free attractions to "get your money's worth").

London is tricky: many top attractions are free, but those that aren't free tend to be expensive (£15-25). There's little middle ground (things that cost, say, £5-10).

If you are not sure you are seeing enough to make the pass worthwhile, do look at its list of covered attractions anyway. That's how I found out about the Jewish Museum of London and the Museum of Brands, Packaging, and Advertising, both of which I really liked.

If you aren't getting the pass, note that MANY attractions now have a discount of £1-5 for advance booking. The trick is, for many things, the morning of your visit is far enough "in advance." So, if you're not getting the pass, go to the website of any place you are thinking of visiting but don't want to get advance tickets now. Register now (it's a lot easier on your computer than on a phone!) and keep track of the passwords. Then, when you are there, if you want to see something, you can log in that morning and buy a discount ticket quickly. I used this trick with great success for Greenwich. It was a nice day so I decided to go that morning; the advance ticket for the Cutty Sark and the Royal Observatory saved me £5.25!

In my non-comprehensive research, here are some attractions with discounts for advance booking:

Greenwich sights as above.
Churchill War Rooms
London Transport Museum
Westminster Abbey
St. Paul's Cathedral
Kew Gardens

and look at which of the very few "skip the line" offers you would actually benefit from. My guess is very few, you still have the security line, which nobody skips these days, and most places which actually require a paid ticket give you a discount and skip the ticket line privileges simply by buying ahead and printing out at home.

Without knowing exactly which places are top of your list - which are achievable in the short time the pass will be valid - it is difficult to know positively what the best answer is for you.

Taking Harold's list as accurate - I'm sure it is - that's even less reason to find yourself under the "skip the line" hocus pocus.

My opinions -

Tower Bridge Exhibition - do you really want that? See the bridge as a bridge, maybe even watch it open and close (schedules are available) rather than from inside a bascule

St. Paul's Cathedral - I go there frequently and any line is usually short and fast moving - use the free (included in the price) verger tour

Hampton Court Palace - I'm a member there and see few queues, even when it is quite busy. It is actually better to go in via the ticket office because you get a nice map of the place and sometimes as you cross into the first courtyard the maps available aren't the ones you may want. Plan plenty of time there. The food is excellent, healthy and reasonably priced, there are many sections to the Palace, and the gardens - many of them, plus the world famous maze - are all included in the ticket

London Zoo - do you really want to go there? I only see long queues there on bank holidays and summer weekends

London Bridge Experience - all these years living here, man and boy, and I've never had the slightest interest in such a thing. London Bridge is just a concrete monstrosity. Different strokes for different folks, I suppose. I wonder what they say.

Kew Gardens - I'm a member and have rarely seen any queue there. They have lots of ticket kiosks and open more as needed.
Plan plenty of time.

None of these comments refer to the buy ahead at home for a discount idea, which is an excellent idea.

I made a list of all the places I wanted to visit and their online ticket prices. Then compared that with what is offered on the London Pass. For the attractions that matched up, it came out to about even and I had lots on my list that wasn't covered under the Pass. So for me, it wasn't worth it. I also don't like rushing from place to place. Want to just take my time and not worry about hurrying to the next attraction.

I used the London Pass and it gave me ease of use and good value. I did take the time to figure out the cost of those places I wanted to see and the cost of the pass. It was the Costco travel offer of the 4 day pass for the price of 3 that made the pass cost saving. . I was also a solo traveler so possible “ 2 for 1” coupons had nothing to offer me.

A different aspect of the pass is its flexibility and the possibility to try new sights that might not have been on the radar before. For example, after I went to the Tower of London, I felt like some time off my feet and took the included river cruise to Greenwich. There I noticed the Cutty Sark and that it was covered on my pass. I toured it and thoroughly enjoyed it. May not have done so otherwise.

The Shard was an attraction I would not have paid individual admission to. I went to it briefly after dinner one night since it was included and enjoyed the views.

Your best bet is to price your “must see” sights out and then compare the prices and make the decision for yourself. Do look at purchasing through Costco if interested. I am guessing that most of the advice you have received on this forum comes from people who have never actually priced out their trip plans and compared.

A note about "free" museums: Yes, the national galleries are free, at least for the permanent collections. The special shows, which draw the crowds, can carry a hefty admission price.