Andrew Potter digs deep into his pockets for the ride from Heathrow to Paddington Station.
The train: British Rail Class 332, built by Siemens, powered by your freshly-withdrawn pounds (and you'll need plenty).
Price: $44 one way, $74 return. Or $112 return if you choose business class, which you don't need to because ...
Duration: Fifteen minutes. That's $2.90 a minute for a regular fare, making the Heathrow Express one of the world's most expensive railway lines.
My seat: Mine is purple, which I seem to remember is the colour of calm, an emotion you'll struggle to maintain if you've not seen the price before boarding.
Fellow passengers: The Heathrow Express slogan is "The Smarter Way", and there are a few swanky European business types on here, the ones who can pull off wearing those suede loafers with the little gold buckle things across the top. It's a look that says "I'm more successful than you", as if having the cash to ride the Heathrow Express wasn't proof enough.
How full: Quite full, but virtually empty by the sardine-tin standard of most British trains.
Entertainment: The Heathrow Express would be a great place to display short films. Instead the TV screens show a minor celebrity pushing some product or another.
The service: Your ticket is checked with cheery efficiency. You can buy tickets within Heathrow Airport or on the train itself, although they're more expensive once you're rolling.
Food and drink: Unless you bring your own, forget it.
Toilets: Not that I saw, but that's not to say they're not there. With only 15 minutes to play with there's not much time to look around.
Luggage: Large shelves for big bags are located by the doors, then there are tasteful glass overhead racks for smaller items. Plenty of room.
The airport experience: All the major terminals have tunnels that eventually snake their way to the minimalist concrete platform of the Heathrow Express. It can be quite a walk, but hey, Heathrow is a big place.
Would I ride again? There's no denying the Heathrow Express is the quickest way to get into central London after a long flight. But it's eye-wateringly expensive. If you're travelling with a friend you could catch an Uber almost anywhere in London for the price of two tickets. The Tube is another option - it's a longer journey, but much cheaper. So yes, I'd ride it again, so long as someone else was paying.