If you are ever in that situation again, just tell them you only have a credit card, nothing else.

Of course, only do that at the end of the ride.

They are not allowed to pick up passengers if the machine (or meter, or lots of other things) is broken. If it’s genuinely broken and you still want to pay, you can call the number displayed below the machine and pay over the phone.

It's a corrupt industry that deserves to die

It's not corrupt. It's a straight up mob, that moans about their "rights".

This is good to know for London specifically.

It's not as satisfying as yours but my general technique that works everywhere in the world where cabs are competing is: ask them if they take credit cards and their reader is working before you get into the cab. If they say no you find another cab. (In my experience they never say no anyway. But I learned to do this every single time I use a cab anywhere because this scam is so unbelievably common everywhere in the world.)

My general technique is to use Uber, or pre-book a cab from the office. I have to admit I was stuck last time I was in Beijing, and of course nobody* takes cash in Beijing.

Yep indeed, I've asked before I got in. In this case I was getting a cab from the airport after a long haul flight. I'd normally use Uber but to try and speed things up I took a black cab because they're allowed use bus lanes and it was 9am.

Yeah as the other poster said, asking before getting in the cab is the other solution. Honestly the hassle of knowing it can happen, or wondering if yhe driver is going to be an ass about it makes it not worthwhile when I can tap a button and have an Uber appear for the same price, and _knoe_ my payment method (amex, to make things worse) will be accepted.

They're breaking TFL rules and shouldn't be operating in that case, congratulations you just got a free ride.

That's great to know the rules are on my side, but the last thing I want is an argument with a driver who has already decided he's breaking the rules. What's the dispute process for a black cab if I'm sitting outside my door with a £30 fare racking up and an angry driver? With Uber, I say "thanks" and type a message when I get back to the apartment and it's handled. With black cabs it looks like I have to phone them. Presumably I also need a receipt or at least a cab number too?

Or a very threatening taxi driver when you point that out...

I miss 2012.

I got on Uber really early and cashed in big time on those sweet £20 bonuses for EVERY referral.

I'd just stand up at the end of a party and shout "WHO WANTS TO GET HOME FOR FREE" and be set for taxis for the next month or so.