securing credit cards while using for Tube and busses

What do you use at home?

I used this for the first time this spring, and it works well.
My Baggallini crossbody came with a hook on a strap attached in the main compartment, and I attached this tiny "wallet."
https://www.lesportsac.com/collections/accessories/products/4009-u254
A card in one of the open pockets is protected, but easy to fish out and use.

Won't be the answer for everyone, but worked for me.

At home in the US, most people aren't using public transportation every day, especially tapping in/out with a CC.

Load the card you want to use for tube and buses onto ApplePay or the Android equivalent and use your phone to tap in and out as necessary. If you keep your phone on a lanyard then you have that security as well as the extra security of using ApplePay instead of your actual card. And really, the rate of pickpocketing in the UK is very low, just be careful and sensible (ie, don’t hang your bag on the back of your chair etc).

In all honesty in probably thousands of taps in and out I've not even come close to dropping a card, let alone lose one. Withdraw the card, tap and replace takes seconds, and (on the Underground) this is taking place in an area smothered in CCTV. Pickpockets are looking for much easier options.

Abroad I always use a preloaded card - so it operates like a bank account but is only good for what's on it. It's also on an app so can be blocked in seconds if ever required.

You said you are "concerned about losing cards".
So for the tube and bus, get an Oyster card.
It will have a set amount on it--20, 30, or 40 pounds--so if it is lost, you're just out that.
Using your credit card or phone to tap in and out on the tube is the new and "modern" way to do it.
I'm old fashioned, so I use the Oyster card, which I've used for years.

On the tube, you tap in and tap out.
When riding London buses, tap in when you get on but DO NOT tap out when you get off.

Another means of transportation in London is the Uber/Thames Clipper riverboats. Tap in when you get on, tap out when you get off. Another reason I'm glad I use the Oyster card to do this.....their tap pad is at the boarding point of the boat.....meaning if you fumble and drop your phone or credit card, it might go into the river. I try not to, but if I lost an Oyster card this way, it wouldn't be any big deal.
Losing phone or credit card this way would be a big deal.

Using Oyster card for transportation means I can leave my credit card in my hidden money belt until I need it for a purchase.
Then I go into a restroom, remove the credit card, go make my purchase and some time later, return the credit card to the money belt.
https://store.ricksteves.com/shop/travel-accessories/security

You might not be using a card on public transport but surely you are using your cards for all sorts of other purposes in all sorts of places, many of them probably less secure than a tube station?

Don’t be overly worried about this. Thousands and thousands of people use cards this way every day and any disasters are really pretty rare. You’ll be absolutely fine.

Just keep hold of your card like anywhere else.

At home I use a credit card outside my apartment about twice a week, on average. When I travel, I use a card many times a day. That is a very real difference.

I use an Oyster Card in London and will give it up only when forced to do so. I have a long, sad history of losing credit cards. Being able to tap to pay is helping.

Exactly, acraven.
Both parts.

acraven, I agree with both parts of what you said.
I have lost credit cards, too.
I keep my Oyster card tucked into my front jeans pocket and access it easily whenever it is needed.

I use my credit card to tap on and off public transport at home and in London, but if you are concerned, stick to a prepaid card for transport and keep your credit card separate. Revolut and Wise are two good options. No need to buy an Oyster card, which is limited to transport in London only.

I am in Southern England now, really do not find it much of an issue. I do use my phone for most transactions, but will use my card as well. For you, it might help to get a sleeve like what are available for the Oyster card, but use for your credit card, keeping that in your front pocket. It will be handy for tapping, you will not need to dig it out of a wallet or purse, and slip it back in your pocket. It will be a little larger than a credit card, I suppose hide whether it is a credit card or Oyster card, and protect it to a degree, being slim, it will not be obvious in your pocket.

We have used tap almost exclusively, the exceptions were for a hotel and a rental car (over 100 GBP), and we did run into a laundry and a parking pay point that were coins only. We did run into a hotel, a couple restaurants, and a harbor ferry, that were cashless.

I used my CC a lot last week for tapping in/out. I stopped off to the side out of “traffic” to pull it out of my wallet in an internal zippered pocket of my small Baggallini. I tapped thru the turnstile, went to the walk, again out if traffic, put it back in on the short side so it was sticking up, re-zipped and was on my way. Reversed at the tap out end. Just because the locals are rushing doesn’t mean you can’t find a spot out of the flow to “tend to business.” Hugging next to a pillar or wall worked fine.

I did put my cc in my pocket when I was wearing jeans but my travel pants are looser and I didn’t feel as secure.