How to shut down Windows 10 PC after Reset

I've just reset a Windows 10 PC, in order to pass it on to someone else. It's a Microsoft Surface Pro 4.

It's now prompting me to set it up, starting with selecting the language.

I want to shut it down, to send it on to its next owner, who will do the set-up.

No amount of holding down the power button is actually turning it off.

Are there any tricks, please?

(I'm worried that if I let the battery go flat, and it won't boot, it might be considered a security risk if investigated in the post)

Try pressing SHIFT+F10 to get a Command Prompt. Note that if you have a laptop, you may need to hold Fn as well.

If you have a touchscreen device without a hardware keyboard, tap on the Accessibility icon to open the On-screen Keyboard. Tap on Shift, Fn, F10.

Once you have a Command Prompt window, run shutdown /s /t 0.